The reason he did that is because cal, like most others in his profession, believe the shorter the rotation the better your team will be. Statistics and heart rate don't really mean anything to me. Cals only championship had a core of 6 guys. The proof is in the result.
I do agree we were worse as we went away from the platoons. But we don't really know why as far as proof goes. It could easily be the continuity I was talking about. The team was used to playing that way. It doesn't mean it was the best way to go from start to finish. The shorter the roster, the easier the management aspect is, the more time your best players receive etc. cal only platooned because he was forced to platoon.
If platooning was better than a short rotation, cal would have picked up that by now. He knows it's not, and that's why he won't do it again, without a ton of returnees. We will play a small rotation.
First of all, the reason most coaches in the profession use a shorter rotation than a longer one is that generally teams aren't blessed to have the type of talented depth that the 2014-15 team had. If you have high-caliber players starting for you but there's a steep dropoff beyond that, then of course you're going to try to play the more talented players as many minutes as you can get. But when you have a bench that is as talented (or very nearly as talented) then you have to think differently.
Secondly, there's a lot of merit to the idea you stated which is
"the shorter the rotation the better your team will be." That's very reasonable if you have a cohesive unit that can practice and play together and get better through the course of the year. Assuming they have the talent and play well together on the court, then it's perfectly reasonable that such a unit can play like a well-oiled machine and be very difficult to beat at the end of the year.
Of course the problem with this is that playing five guys exclusively for an entire game (or at least the majority of the game) takes a toll physically, and is hard for them to maintain defensive pressure consistently due to fatigue. Also playing so many minutes makes it difficult to maintain the lineup due to foul issues etc.
So while playing a tight five man unit is a laudable goal, it runs into practical problems achieving that during games and over the course of the season.
But what if I said that there was a way that one could achieve this magical five-man squad without encountering a lot of the downsides that inevitably arise? Would you be intrigued?
And of course the answer is to use platoons! Doing so with two distinct five-man units, one can actually have the best of both worlds. You can have two tight units who practice and play together and hopefully improve their execution and effectiveness during the course of the year. At the same time because there are two of them they have the luxury of not getting tired, and are thus able to maintain their defensive intensity throughout the entire game!
So you actually prove my point. You (and others who were against the platoons at the time) seem to be stuck in the habit of how most teams of the past have played (nearly all of whom who did not have nearly the talent the 2014-15 team had) to recognize that playing a different way actually can improve a team's effectiveness well beyond what others can achieve playing a more traditional way (and again, the stats clearly bear that out.)
BTW, having not one but two well-oiled units was exactly what I was hoping Calipari would spend his time developing that season. In fact I was kind of hoping they would have completely different styles and plays tailored for each squad. For example I always envisioned it as a boxing match, where one round the fighter comes out and lands crushing body blows (which I kind of envisioned the blue squad doing by working the ball inside and driving the ball to the basket with the Harrisons), and then the next round the boxer comes out quick on his feet and has lightning jabs (which I kind of envisioned the white squad forcing the tempo, shooting a lot of threes and pressing etc.)
It's hard enough for an opposing team to prepare for one well-oiled team, but nearly impossible to do so for two, especially if they're playing different styles and with different pace. That scenario was a very real possibility that year, if it had been handled correctly.