I agree with @Olly_Thomas and @Gergely_Komives, it is very important that if this feature is created, it should be a user-selectable option only, giving the user the choice to either base training loads on the auto-generated eFTP, or the user manually-entered FTP value.
Personally I don’t want TSS/ATL/CTL calculated based on the eFTP value, since I know that my true FTP is (definitely) just a little bit higher than its estimate, even though I do put in hard training efforts and I am aware the algorithm also presumably draws data from sub-maximimal/sub-FTP changes/output in HR/power to derive its estimate. The fact is doing an all-out FTP test is extremely intense, particularly psychologically, and the reality is that training efforts will always be somewhat below true max test efforts.
Let me put it another way. Consider your current best eFTP based on your training so far. Now, imagine that next week, you were invited into a training room with a perfectly calibrated Wattbike (or whatever), and were given an FTP effort/test protocol, but with the watts set a few percentage points higher, say 5W-10W. In front of the test bike is a suitcase filled with ÂŁ10,000,000 in cash, of totally legitimate origin. The cash is yours if you can complete the effort for the new target FTP. (Suppose some stupidly rich person just finds it entertaining to watch some ordinary person do an all-out effort for one hour).
I’m willing to bet that for 99% of you, you’d be able to do it; spittle drooling off your face, in a terrible state, and ready to basically collapse/throw up everywhere immediately afterward. The point is that this is a true 100% FTP effort, and the reality is only under the most extreme motivational conditions (e.g. the scenario described, a TT effort when you know you’re in contention for the win, a race where you’re in a small leading group, a chance of a professional contract with Team Ineos, whatever it is that really would drive you) can you truly do your max effort, because it is nothing except absolute total unmitigated suffering till the very last second.
So I’d rather be able to base training loads on an FTP value that I realistically appraise is my true physiological potential at the time, rather than the eFTP which for me is always just fractionally conservative. This is every more true if you have several years of training under your belt, as you begin to know your own body so well and get pretty good at judging exactly where you are compared against previous best-efforts.