That’s always a difficult way of going about things. An aero frame DOES WORK. It is more aerodynamically efficient or in other words, faster for the same power. Considering the average speed that especially the pros and top amateurs are going, aero gains will likely be the most important out of aero, rolling resistance and weight.
The gains are however in the 5 to 15 Watt range (just looking at rim/ fork profiles and shielding of bottles is probably closer to 5 watts at 20mph+, and narrow handle bars that make the rider more aero will add the rest.
So if it was say 10 watts between a BMC Kaius and a Specialized Crux, that would hardly mean BMC sponsored riders would automatically dominate every race. Especially since gravel also has a lot of external influences like punctures, chain drops, drive trains getting completely gunked up etc.
I see most people bending it around the handle bar or head tube. Officially not allowed, but usually not enforced either. Dylan Johnson does this now:
If he can get away with it, being a highly scrutinized professional, I as a mid pack rider probably could as well…
I do agree with aero not being the thing that should override every other quality of a bike.
What does a Factor Ostro‘s aero saving help you, if the frame is too harsh for your liking, and you have to stop two more times than you would have on another frame?
What does a BMC Kaius‘ aero handle bar do for you, if you need 45s for your course, and they do not fit into the frame?
But that can be said for every bike.
I think an aero gravel bike CAN be the best choice for Gravel racing, especially with flatter events (I‘d even count Unbound towards these) or very high speed events like the UCI Gravel World Series.
If it’s best for your particular case is obviously a different story.