I suspect that many go into Ramp tests expecting some certain FTP improvement, and therefore expect things to be easier at certain parts of the Ramp. Most know going in that they get a bump in FTP at 19:30, so if you’re expecting some 2-10% jump in FTP, correspondingly you might expect 19:30 to hit and the effort to still feel much easier, or at least markedly more tolerable, than before.
Instead, when you’re already fit - as many of the people who have done 8 ramp tests and two full seasons of TR undoubtedly are - the gains are in the margins. A 2-watt or 5-watt increase will feel the exact same at 19:30, and it might feel worse based on rest, fueling, sleep, work, kids, etc. I think, as you said Chad, you have to go into the ramp tests as it were a race: “This is going to be really hard, and I’m going to have to bury myself to get an accurate result.” If you go in thinking, “I’m going to get to 21:00 this time, no problem”, and 19:30 hits and feels really hard, you are far more likely to check out earlier and misexpress your true physiological capability.
Finally, I know ego is a real thing, but I think a lot of people are way too hard on themselves when they get a marginal decrease in FTP based on testing. These tests are fungible IMO, and there is error associated with them, and many factors contributing. A 2-watt decrease in FTP from a ramp test followed by a 15W increase from an 8-minute test doesn’t necessarily mean the ramp test doesn’t work for you. It could be as simple as your ramp test result pissed you off and properly motivated you coming into the 8-minute test after you weren’t properly prepared in some way for that ramp test. I think this is way more likely the case than otherwise for a large number of users who are quick to dismiss the ramp test protocol based on a disappointing result.
TL;DR - it is a hell of a lot easier to mentally tap out of a ramp test than it is to complete it to physical failure, and I think that happens more often than we want to admit.