Someone else mentioned them, I thought you were also mentioning them:
"AP preview days pre covid reopening through today" is not the most graceful of phrases. I thought you somehow trying to compare Galaxy's Edge or Pandora AP previews to Guardians AP previews, which obviously made no sense.
But, wait, you "disagree on both", including this? (I'm trying to figure out what "disagree on both" means.)
You don't think they're using the park reservation system to keep lines and experiences more manageable? Or you don't see that as a benefit?
Also - when I say that it "tells me the parks are busy" - I mean that in the general sense, as far as "busy periods", not that a specific park will be busy on a day that it's sold out. If I'm deciding between weeks, and I notice that one of them has more "sell outs" than the other, then I pick the latter.
I agree with everyone else - there isn't a direct correlation between "sold out" and "busy park" - for example, I was there a couple of days before Christmas last year, and walked into a nearly-dead MK that afternoon. (Because of rain. It was slammed that night, however.)