Headbites do not equal=eating flesh. According to the anchorpoint essays they don't eat people, but have function like a biological battery of sorts, due to the chemicals that make up their blood..etc.
So some random dude on the internet making stuff up about the aliens is ok, but we have to bash directors who do?
well at least the guy who made the anchorpoint essay site, makes sense in terms of the reasoning he comes up with for things, even if its also not established to be canon due to not being confirmed in a film.
its funny how the strause's keep defending other bullshit by saying "the aliens aren't simple bugs" but then want to reduce them to such in other instances. The aliens are alien and we don't know that they have to breathe the same way we do either, as they can exist in a vacuum, and they don't require oxygen. If they can do that and live, who says they need to consume meat in order to sustain themselves.
It seems their inner jaw and how its connected to their mouth on the inside would limit the size/amount of flesh that could be consumed at any given time and thus is not very efficient for that, so its a defense/offensive killing trait it evolved as opposed to an aid in mastication. (no not masturbation.)
In the event of the space jockey's creating the aliens, they surely could be biomechanical and not have to eat things. They would be part biological part machine in some sense. Organic, replicating semi-machinery in some regards.