Holidays can explain it. In my opinion I see each of the three franchises as their own canon. So if AvP is good enough I might include it in each. I am hoping A:CM will be good enough to consider it canon for after ALIENS and ALIEN 3. For Predators canon, we may have to wait and see how the new movies comes along for all we know it could turn everything that was made for AvP3 wrong. Lets just hope that does not happen.