Most importantly, flipped classrooms tend to really benefit students. I had a teacher try it out this year, and there were some complaints about the lectures (Khan academy) but not the system. I hope that the author simply wasn't aware of the effects on students. I can understand that author, as a professor, would be worried about his career, and those of his pers, but as a student, I believe the teacher should always put the learning and well-being of the students first. If flipped classrooms have the potential to really benefit students, teachers and professors should look really hard to find a way to make them work, even at some potential risk to themselves.

There's a professor at my university in chemical education who works a lot with the flipped classroom setup. He's done quarter vs. quarter comparisons of his class' performance for flipped vs. traditional setups in intro-level chemistry courses. He sees modest increases in overall scoring of the flipped class' midterms and finals. He makes self-depreciating jabs about it when he gives seminars on the topic like "you see there's an irrefutable increase in the scores of the flipped classroom, unless you're a statistician then it's very refutable".

Basically, data suggests the flipped classroom is at least not worse than a traditional setup. Hopefully the flipped version encourages more problem solving and engagement with the topic. The only flipped classroom I took as an undergraduate was poorly implemented, where the setup basically made sure that you had to put in much more time than your standard class to keep up. The class was notoriously disliked and students performed poorly in it.

Experiences like that make me wonder, though, if there's a more pessimistic perspective on why there's so little difference between flipped and traditional classroom performances: we all know there are a lot of students that sit through lecture (or don't) and get nothing from it. I attended all my lectures consistently and there were still quite a few that were like that for me. Maybe the average student just doesn't actually get that much out of lectures and gain most of the understanding on their own time anyways, then of course the flipped classroom would perform similarly to traditional ones if that were the case.