I mean, when a main designer of your game talks about how this mechanic (1UPT) was bad, he was wrong for including it in the Civ V, and that his next game will include unit stacking, you'd think someone would notice. But apparently not.
Did you actually read what he wrote in that?
This was a model very much inspired by the old wargame Panzer General. On the whole, I would say that the combat mechanics are indeed better in Civ 5 than in any other entry in the series.
I do think that 1UPT can work in a game, but you kind of have to bend the game around IT. In Civ 5 the fit was a bit rough, and it showed, but that's not why I'm going a different direction in ATG. I just enjoy experimenting with new ideas and seeing where things end up. I'm sure my next game after ATG will go in yet another a completely different direction!
What he wrote was nothing like what you said his thoughts on 1UPT are
Given how the developers usually defend their work in spite of everything (like Bioware with its ME3 ending clusterfuck), the very existence of criticism - and, most crucially, the fact that his next game rejects the 1UPT completely - speaks volumes about how he really feels about it.
Yes, 1UPT may work in Panzer General. But it didn't work in Civ V, and, despite anything he says, it will never work out, because you either have too little units, and then it doesn't matter at all, or too much units, and then it's blanket of doom time and a fun-drain, and there is a very small middle ground in between those two that is completely impossible to reach in a 4x game like Civ 5, thanks to the "we equally support all playstyles, from sprawling mega-empires to 3 city tall kingdoms" motto.
It's just completely, physically, impossible to do without fundamentally changing production mechanics. And then it would stop being "Civilization" at
all.