The "devs are lazy", as ridiculous as it may sound, can make some sense for games that completely lack AF, but I find it veeeery hard to believe that devs would go through the trouble of adding AF but would choose for whatever reason to stick with low amounts of AF, instead of full 16X.
And when exclusive games with great graphics have variable AF, it makes it pretty clear that it's not as simple as "it's just devs not using it". I'm not a programmer myself, but I assume having variable AF depending on how demanding the scene is takes a lot more work than just setting AF to 16x and having no performance issues for that.
I'm not saying that's it's a definitive solution, but as for what we know now at this moment, it appears to be more of a blatant problem selective with certain games. Perhaps it's a problem with implementation, but it can be done on PS4, so the issue seems to be on why it's apparently so difficult, not "The PS4 is broken Sony owes me!" (You aren't saying this by the way, there's just a tendency to overreact I think).
There is definitely a curious thing going on here though, but I'm more perplexed by why games like this, or Revelations 2, even REmake Remastered are having quirks with the PS4 primarily when they should run easily. There's a connector between all 3 of these, so that indicates to me maybe it's a 70/30 split between dev optimization and potential hardware difficulties.
People are actually buying this? I have this on PS3 thanks to PS+ and never felt the urge to fire it up.
I'm sure they made this HD version on a shoestring budget.
Some people like fun games
If it wasn't a DMC game, I don't think there would be nearly the amount of (undeserved) flak this game got.
Your second statement is probably true though- epitome of hit and miss with some of these HD upgrades, but this is sounding like a good one.