I agree with the other answers: the issues is in the difference in power measurents between Wattbike and the trainer.
Something that was not yet mentioned but may be good to remember when discussing about this subject: if the test is technically ok, you should not be able to test too high. This has been stated several times in the podcast.
It may seem like your FTP is set too high, e.g., when doing VO2Max intervals; but that’s just because your power at maximum oxigen uptake is lower than what people generally have (when compared to your FTP).