I would have to look at individual play by play, and I just don't have time for that unfortunately. Also, it was the author's premise that Watkins FC/40 was the basis for his foul trouble. If Watkins had a serious fouling issue, it's not recognized in this stat, and it's not really recognized when you compare him with the team either.
His 4.2 FC/40 is 5th on the team for guys who saw rotation minutes, and it was .3 off of Lamar Stevens (3.9 FC/40). Sure, sometimes they picked up 2nd fouls in the 1st half or 3rd fouls early in the 2nd half, but that doesn't show someone has a propensity for fouling. These things happen, especially when someone is a shot blocker like Watkins. I would guess that Lamar's 3.9 FC/40 won't be seen as a problem when they give a grade for him, so why is this .3 difference relevant for Mike? That's 3 more fouls per 10 games, that's a small difference.
Mike was also 5th on the team in minutes (it also seemed clear that he needs to work on his conditioning a bit), and I disagree with you that "foul trouble isn't always picking up a 4th foul or fouling out of games." I think while your point could make sense in the abstract, it doesn't pass in practicality.
If Watkins is really foul prone, then why didn't he foul out at all or pick up a 4th foul often? How often was he in games at the end? I'd guess he was probably in end of game rotations 75-80% (maybe more) of the time, so why didn't he pick up more fouls in those spots? If he was foul prone, then why doesn't his end of game fouling carry over to a 4th and 5th foul? If he picked up an early 3rd foul in the 2nd half, but was able to play the last 10 minutes or so, did it drastically impact the course of the game? This is why I don't think this passes the smell test.
We need to appreciate and understand statistics in basketball better. Watkins had some foul trouble in some games this year, but he's not foul prone, and he never fouled out! Sometimes the efficient answer is obvious and we don't need to go searching for answers that lead us right back to where we start.
I think there are quite a few obvious things for Mike to work on: i.e. better defensive positioning in the low post (felt like he often was beaten to spots and gave up good positioning too often, this was obvious against guys like Bryant, Ward), work on that drop step to his left for the right handed hook, and physical conditioning/strength. He's a shot blocker, he will commit fouls, but he was not foul prone last year.