Pomeroy’s conclusion absolutely fits common sense. The more open looks a team gives up, the more threes an opponent will take. Therefor, over a season, it’s a much better way to measure how good a team is at preventing open looks, which is how one would measure a team’s three point defense. I mean Pomeroy and the other links I’ve provided prove this statistically, showing that there is a correlation but it’s less than 2%. Unless you have something math wise to back this up then I don’t see how this is controversial.
Also I don’t know what your point about MSU is trying to say. First of all I’m pretty sure your numbers are wrong. They didn’t lead the Big Ten either of the years, the were 2nd in 2015 and 3rd in 2016. I assume you’re talking only Big Ten play since earlier you made a point about how his conclusion was wrong since he counted non conference too which has variable schedules. The difference between MSU and the worst 3PT% defense those two years was 6% and 7%, respectively. With margins that small I 100% believe it was luck that Michigan State opponents happened to shoot 3% worse than the mean those two years.