I am in agreement if you don’t know what you are doing you should round down!!! If you do know what you are trying to accomplish you can always just pick the right workout% for the FTP you have… The primary way I would do that (if I was working harder) would be through HRV monitoring, highly accurate for me as well as sleeping HR. And if recovery is taking too long then I would lower my targets. As a coach it is probably easier to lower peoples FTP and have everyone doing the same workouts.
For precision, recovery is highly individual and needs a more systematic approach such as HRV, individual monitoring or testing. If you are not recovering enough you should lower your target (or your FTP…) So if Jeremy likes a 90% target, he could switch all his students to a ramp test and change it to 85%. A ramp test does have the tendency to go high, and a 20m test is more likely to go low. So I agree to be safe without predictable monitoring then it’s better to go low.