It is if the changes better reflect what that CR is supposed to be. But it ultimately doesn't matter much. D&D isn't balanced well enough for it to matter, unless the to-hit and HP were VASTLY different.
I think you're correct in saying that there needs to be less variability for CR to work better. The problem I see with that is that it is really hard to give unique, fun abilities to classes and accomplish that goal. I think that the cure would likely be less fun than the illness.
it might be, which is why I wrote that this might not be better / wanted.
It’s a matter of what your goals are, encounter math that actually works reasonable well, with the costs this brings -> the PF2 direction. Bounded accuracy and monsters being applicable for a wider range of levels -> slight improvements to the 5e math, but it will never be precise
While I am typically critical of WotC not taking advantage of all the available tools we have these days, I do think that a robust statistical analysis system is fairly beyond their budget and expertise.
They should be better at CR than they are, and it's possible to build a tool that cam analyze things, but I don't consider it a mark against them that they're relying on simpler, fuzzier methods in this case.