CX is it’s own discipline and has no correlation to gravel. Are there similarities? Certainly, but they are, in fact, very different disciplines.
If you want “short-course gravel” races, speak to race organizers. But there is no need to abandon CX as it currently exists.
I thought he was talking about a proper cx course where you’re running 25psi on a grass or unsmoothed dirt surface. Here, the fattest (of top spec) would be faster than a 33, 35, 38, 42… all the way up to an XC mtb tire even in the dry. Once the surface is groomed/smoothed mechanically/plowed, sub-40 is faster. Without that, the series of small bumps will slow you down. Most ‘gravel’ surfaces you’re thinking of have had a plow go through there at some point in the road/paths life.
Blasphemy.
I don’t get your point. Are you basically saying that when the mtb came out, CX missed the boat by not switching to riding MTBs instead of CX-road bikes with knobby tires? Wouldn’t that make the invention of gravel bikes the stupid thing (relative to the original -no shock MTBs)?
Go back and look at the original post…he included pictures of the trails he would be riding.
Yes. Any sport/discipline where you’re purposely using bad equipment is stupid. The only exception is if it’s a whole broad category (sailboat v powerboat; bike vs motorcycle)
Cross bikes are very suited to cross conditions. American-style gravel is extremely rare in typical (European) cross. If you don’t ride in cross conditions, another bike/tyre choice might be faster, but that doesn’t mean cross bikes are outdated.
I’ve had good races like the conditions in OP pictures with 33mm but next year I’m going for 35mm. We have some rough root sections on a couple of our CX courses.
Gravel elitism, it was bound to happen eventually lol. Idk what else to tell besides no you’re wrong. We race road bikes with tires smaller than necessary all the time. People consistently under-bike with gravel bikes on mtb trails all the time for a sense of challenge. You may not, but it is very common.
But tbh, I can tell from how you are speaking, you just aren’t a cross racer and have probably never even been on a cross course. A typical grass cx course (especially of the euro variant) will be about the fastest on a 35mm tire with the right pressure. Plenty of American courses are too mtb-y , but that is a whole other discussion.
If it is real cross conditions muddy where the tire is sunk in the mud I feel like a wider tire must require more watts for the same speed in a straight line. You don’t want to float and spin on the soft mud and push through more of it, you want to get down to more solid ground and slice through with less resistance on the narrower 33. On a corner maybe the wider tire allows you to go a little faster (although I think proper skill on 33 would be the same), but I don’t think the cornering gains would overcome the significant difference in watts to power forward.
In summary my guess at what is best is: wider for dry, narrow for muddy. Switching is too much effort all season so I use 33s.
I had an On-One frame that I set up single speed with WTB Riddler 37mm tyres. They were good both on and off road, only really coming to grief in sloppy mud.
European CX courses are often muddy so you are often better with a narrower tyre to cut through the surface slop and get grip in the substrate. If you want proof - just go and ride a fat bike in those conditions 
Certainly in the UK we don’t get the miles and miles of gravel that you’d recognise Stateside.
I’m running this question round in my head. New to cross. Bike currently setup on 33mm Challenge Baby limus tubeless with Inserts. Loads of rain in the UK this week and race on Sunday will be muddy (grass airfield + woodlands that will get ripped up in the race)
I’ve just fitted some new 45mm Vittoria terreno wet tyres which I plan to run at 22/21 psi (tubeless & inserts).
Clearance looks a bit tight on the frame (about 5mm tightest either side of the chainstays at the back on my supersix evo cx) so I have ordered the same tyres in a 38mm which I may experiment with the day before.
Really interested in people’s feelings on the whole wide tyre in mud debate… Didn’t think about the prospect of the tyre floating on the surface of the mud rather than digging in. Makes sense… Now very confused!
CX is the racewalking of cycling, it’s raison d’etre is to make it harder than necessary.
I could go on and on and on.
Put more simply, you just don’t get it. And that’s fine.
And to answer the original question: it absolutely depends on the course. Wider tyres are not great in mud as they slide on top instead of digging down. Thread pattern and how much mud sticks on them is another factor. On rough, fast and dry courses, go bigger if rules and frame allows.
You don’t want wide tyres in the mud. If its limus terrain, stick with the 33s. Wide tyres just create extra drag.
If it’s hard and gravelly wider will help. Also maybe if its mainly hard, but with lots if rocks and roots.
And you absolutely want to have as much clearance as possible if its muddy.
The drag isnt the problem a lot of the time in mud. its the grip.
If narrow tyres were faster, there wouldn’t be a width rule in the first place.
Wider, chunkier tyres have more grip and can be run at lower pressures, they are faster.
We had this debate before, and sorry no, I disagree. Wider tyres are not faster when it’s really muddy.
Happy for everyone to turn up on their MTBs in my races to prove me wrong 
Wider tires in mud will likely hold more weight of mud and thats not a good time. I have some 33-35mm tires that hold onto tons of mud, and other tires that shed well. Baby limus sheds well for me, Regular limus also sheds well but grips better. Grifo holds onto a lot of mud for me.
The 38mm Terreno Wets arrived yesterday. Fitted them last night and they look like a good compromise. Emphasise the ‘look’ at the moment - clearance better and seems like a reasonable balance.
I will let you know how I get on…the proof is in the ride. Will be trying a range of pressures in the practice laps starting at 23/22 and going lower.
So… The race was yesterday. Course trained quite well on the exposed sections, in the woods there was some thicker sticky mud.
Ended up running 21/20 on the 38mm tyres. Happy with the corner grip and running the tyres low gave me good grip up the steep short muddy climbs and decents.
I did feel that the shoulders of the tyre did pick up a fair amount of the stickier mud that was chewed up on the (ex) grass lines.
Would have loved to have tried a 33mm baby limus tyre just as a basis of comparison.
2 weeks till the next race now. UK heading into rainy season so going to keep on the 38mm for now.