If you hit AiFTP once a month (you were supposed to test every 4-6 weeks, so that seems a reasonable interval to ask TR to reassess), isn’t your ATL/CTL curve going to consistently flatten off unless you continue to ramp volume forever?
If so, what value does it have in understanding how your training is progressing?
Yes, that is a feature, not a bug. Your sustainable training load is separate from your achievable FTP or other fitness metrics. Even if your FTP doesn’t continue to go up CTL should level off for a given sustained volume because you are limited by time and recovery. Its more useful to compare to previous seasons CTL at the same time as well as peak CTL, TSS ramp rate etc to determine how training should proceed.