In 2015 Dr. Andy Coggan* introduced Coggan iLevels to replace Coggan Classic Levels as a result of extensive work showing that power above FTP needs to be individualized (the “i” in iLevels) and is non-linear (i.e. using flat % of FTP for training zones above FTP was no longer appropriate). Simultaneously, he introduced Optimized Intervals where the duration of the interval (a range) and the intensity of the interval (also a range) for intervals above FTP were determined for each person to elicit the appropriate physiological response (e.g. to increase Functional Reserve Capacity, FRC, a measure of how many Kilojoules you have available above FTP).
TR still folllows old school training with the fixed percentage approach. Thus far, Optimized Intervals are only available to users of WK04. If you aren’t a WK04 user, what you can do to compensate is that if you aren’t getting the appropriate training load you feel you need, you can sort of “guess” by increasing the duration and/or intensity via +1, +2, etc or via using Workout Creator to modify your workouts.
btw: The above explanation is why some individuals find TR’s “VO2Max” intervals ridiculously hard at the start (typically those with a phenotype of a TTer) and some find them easy (phenotype of sprinter).
*If you are unfamiliar with Dr. Coggan, he is the developer of virtually every important power metric, including TSS, NP, IF, CTL, ATL, FRC, etc.