Plus 25%…
That is 30 seconds on 30 seconds off, with the on at 143% of FTP and the float at top end of Z2… personally I don’t know anyone that would be over tempo HR during that (although there might be some, new to structured training)
It certainly is not an indication that FTP is out, although it might be. Grassy Ridge is not actually a VO2max workout.
PS anything above Threshold is not anchored to FTP anyway. 