I have found that the workouts you mentioned do seem to increase my TTE at FTP.
Since I have done all four FTP Progressions in the SUF program with little difficulty, I am starting to do longer ones. I did 3x15 yesterday at 95% FTP. I made it through, although the last interval, especially the last 5 minutes of it was tough. I probably will repeat that until I feel comfortable, and then move to 2x20.
Remember as well that the Empirical Cylcing podcast also says that many people’s FTP numbers are too high. If you have trouble with those intervals even at 95% of FTP that is probably the case. The reason for the higher numbers and the difficulty is that your test number probably includes a significant anaerobic contribution.