Whether it was intentional or not, whatever the reason for it being there, doesn't change the fact that it *is* there. Of all the movies for a blatant Predator reference to show up in unchecked (accidental or not, doesn't matter), it's in the Alien prequel by Ridley Scott? That's amazing.
That's like finding a Freddy Krueger reference in the original 1980 'Friday the 13th'. It's like if an extra in 'Schindler's List' happened to be wearing Indiana Jones' hat through sheer coincidence. It's like, well,
any of these.
The way I see the tri-laser thing in Prometheus, there's a few scenarios:
1. It happened by accident and (somehow) nobody noticed, despite passing through the hands of numerous movie industry professionals. We noticed it, and we're just random people on the internet. In my book, that makes the filmmakers ignorant.
2. It happened by accident, someone noticed, but somehow had never seen 'Predator' or heard of "AvP" (despite it literally being an unspoken topic during the making of the movie). In my book, that makes them culturally ignorant.
3. It happened by accident, someone noticed, recognized what it could be interpreted as, and left it in anyway because they "didn't care". In my book, that makes them culturally ignorant (although for different reasons) given the nature of the Internet and "fandom". The fact that we're
having this discussion at all is evidence of this, not to mention countless other discussions we've had about all kinds of single-frame minutiae in all of the movies ever since the movies were available for home viewing (and re-viewing and in-depth scrutiny).
4. It happened by accident, someone noticed, recognized what it could be interpreted as, and left it in intentionally. In my book, that makes them brilliant master trolls of the highest order, largely for the same reasons as #3 above.
It's a little bit like Robert Rodriguez openly saying that 'Predators' wasn't going to reference anything other than the first Predator movie, and then it ends up making references to other Predator/AvP material anyway (intentionally or otherwise).