It's quite a fun read but I don't understand why the author chose the word "meat". I mean, if for those aliens human biology is so weird and foreign, how could they have a concept of meat? Or meat flaps? That seems to imply that they're familiar with non-sentient meat, but what would that be? And if those aliens are so different from us they probably don't have the same concept of food as we have, so it wouldn't make…
Indeed, as you've noticed, their revulsion appears to be the thing which prevents them from getting the picture. It's not as if they haven't seen meat. They've even seen intelligent creatures that are almost entirely meat. That's all part of the joke. If these aliens could get past their squick they'd be clever enough to understand squishy brains, but they can't.