They apparently separate things by brand and frankly nobody seemingly told the Predator writers so AVP still occupies a slot on the timeline even if legal doesn't see it that way. It's clumsy and stupid regarding the actual stance Fox has and is left unenforced so it seemingly doesn't even matter. And even if we didn't include the Alien versus Predator films, they still predate the prequels in the Predator continuity by the existence of the skull and Lex's spear, not to mention Neca lore which is supposed to be canon and has a handful of instances where they appear prior to the prequels. The only elements other prequels Predator uses is the Engineers and that's only based on art done by Tristan Jones.
Really the only way around this is a hard reboot where everyone literally is required to start fresh but that's what happens when Fox doesn't pay attention to what it's doing and simply doesn't care.
It's just two continuities Fox has been really bad at implementing.