I hope not as the ramp tests as a 15percentile outlier doesn’t provide for me a realistic FTP. As far as I can tell though AT just needs a FTP figure to start doing its stuff and it wont matter where it comes from.
I haven’t actually tested 20min wise since before the TT season and only changed my FTP manually once given TT results and how workouts were feeling RPEwise and it seems to have coped OK.