I don't think he was, he was pointing out the engineering prowess of Facebook. Essentially, if they can write something as complex as HipHop, they surely could figure out how to properly delete photos.
The point was: PHP is dog slow, Facebook solved that particular problem with a gargantuan engineering feat, deleting photos is trivial by comparison, therefore they either do not give a crap or it's somehow beneficial to them to keep them around forever.
Then I guess I stand by my comment of "please don't make this about PHP", I agree with your main point though.