You won’t find anything about FTP in that article because that’s not where the FTP ramp test originated. There is a podcast that discusses this very issue on the FTP ramp test origination. I don’t recall exactly, but there was a room of guys (maybe Cliff Team or other pro team) to include the TrainerRoad employees (coaches and CEO) and they asked how many people have done the FTP test recently. This was back when there was the 20 minute test and the eight minute test. The room was silent and pretty much everyone agreed it had been a while because the test was not fun to do. I believe this is when one of the Cliff guys said they did a graduated/ramp type test to get their FTP.
The idea of the TrainerRoad FTP ramp test was born. TR did a bunch of tests and tweaked the percentages until they got it right. Then they analyzed their users rides post FTP ramp test for accuracy and performance. 10s of thousands of tests later they finalizesd the TR Ramp Test and released it as the preferred method for their TR users to determine FTP.
I would agree with TR that the ramp test is far superior to the 20 min and 8 min versions. The TR ramp test is less dependent on pacing, experience, fatigue, etc. that plagued the previous tests methods. Not to mention, the FTP ramp test is far less mentally challenging and takes less time to recover from.