Baylor used their posts differently. It wasn't just size, it was how they are used. Same with Gonzaga and UCLA (mostly), same with Houston. All four used 4 out ... and played smaller at the 4 spot.
While a majority of B1G ten teams are still using them in low post back to basket and losing. Mich, Pur, IU, Ill ... and play inside/out ... the teams listed above played outside/in and place their bigs high, facing or rolling or on weakside which is what IU will most likely do next year.
Analytics is pushing this as it's well known that the back to the basket post up is the least efficient play in basketball. Not least efficient shot, but from set up to feed, to shot, the chance of success is lower than driving, rolls, or weakside dump offs.
It also demands a four that can stretch the floor or drive, and be able to guard a larger area, which is why many teams go smaller at that spot. Plus it allows switching on the perimeter.
Read up on 4/1 and how the big is used. Placing TJD on the left side and pounding the ball into him will not be the norm anymore. He'll be in the "dunker spot" on weak side eating up offensive boards, lobs and dunking off dump offs... or rolling off high picks.. and hopefully pick and pop.
As far as depth only need three posts ..I said need. It's better to have more, especially developing. We have 4, 3 play ready, 1 in waiting. Perfect.
Gonzaga only played 2 traditional posts last year with a 3rd in Diallo only getting spot minutes. UCLA only played with 2, Baylor 2, Houston none... all of them were single post with a wing at 4.