Great examples of the Ramp Test and/or 20-minute Test working for some, but not for all.
This week will be the first time I’ve completed both tests for comparison purposes. The 30 watt variance you mentioned your buddy has is exactly the reason I want to give it a try. Having an FTP set incorrectly by ± 30 watts would have a huge impact on training quality … all the more reason I think comparing the two tests could be very valuable.