The ref you linked to explains succinctly the change of density at constant MAP as one climbs. I'm at a loss to understand why you can't accept the explanation as it makes perfect sense. When one goes to altitude, for a given ambient pressure the density is higher. Ergo, when one goes to altitude, for a given MAP the density is higher.
Succinctly, yes but in exhaustive detail, no. just because something makes sense, does not mean that it is correct. I have seen countless times, things that are explained and 'make sense' but are either misleading or outright wrong.
I can take either stance. If I make assumptions, I can 'prove' either side. That should be obvious after reading this thread. However, it's also obvious on here that none of us really know what the answer is. You might actually have the right answer, oggers, but there isn't enough info presented here to definitely say which answer on here, if any, is correct.
My goal is to find the correct answer. If it seems that my initial 'guess' was wrong, I don't care. I'd rather find the correct answer than hold on relentlessly to my initial 'guess' and know I might not be correct.
You still didn't answer my question about where the principles are 'well described'. Or that other question I asked. Can you answer those two questions before we go on?