@CH01
I think you are interpreting the study incorrectly. He’s not giving a general range that is applicable to all cyclists.
Let’s say you grab 10 recreationally fit cyclists. You give them an FTP test. They “score” anywhere between 220-300W. On average they score around 260W. You take another group of cyclists (world tour pros), you give them the same FTP test. They “score” anywhere between 370-430W. On average, around 400W. Remember those averages.
You get invited to several podcasts. The host asks you: “CH01, tell us, what is this FTP of which you speak? Is it the secret sauce?! What’s the range or zone?” You say, well it is anywhere between 260W - 400W (the respective averages for the two groups). The 260W comes from the one group, the 400W comes from the other. 
Would your conclusion as a listener be to train somewhere between 260W and 400W? As in: this guy is telling me my zone is 260W-400W.
No, your conclusion would be “oh, there is a discrete number, not a range…and my number applies to me”. If I choose to, I could then go measure my own FTP and realize I’m 295W (within the range of the recreationally fit cyclists in your study). Or maybe I measure it and “score” 365W (holy crap, get that boy a contract).
What you don’t think is: this guy with his study on the podcast is telling me my FTP range is 260W - 400W, and that is how hard I should ride my bike. ISM is not conveying an individual training range. He’s not saying you CHO1 have a range of 1.3mmol-1.8mmol. He is conveying respective averages of the two groups, the same way you would say “well, it’s anywhere between 260W and 400W”
^^^^ implication that he doesn’t state: yes, and you have to see what yours is yourself. ^^^^^
What might be confusing things is that DrMF is giving his forum readers zones/ranges. He is anchoring those zones based on two discrete values (analogous to how you might base training off of one value: FTP). His values are AT2 and AT4. That means, 2mmol and 4mmol, respectively. (in the old days and now less common: one definition AeT was 2mmol for everybody, and 4mmol for AnT for everybody). If you read Alan Couzens article @sryke posted, he uses inflection points on the curve…much more common (and likely more valid).
Point is: DrMF is providing zones because he is anchoring on a predefined fixed value. ISM is not. You find your own LT1 and create your own zone based on that anchor.
As @sryke and I were discussing higher up in the thread, it’s not important that DrMF uses these (perhaps) outdated definitions of AeT and AnT. It’s the trend and the relationship between them that we’re interested in.