Although for ghouls it's really deviant for them to eat flesh that's still alive

I also wondered about that but maybe the analogy of how folk may prefer cooked meat versus raw. After all, cooked meat does destroy tissue cells, thus, *definitely* dead tissue. For a ghoul, maybe a living person is like 'sushi' to them. ;-)

As to ghoul versus shapeshifter, I'm thinking ghoul is a different 'species' that mimics humans, while a shapeshifter is a human with a genetic trait (e.g. 'hungry hungry hippo guy'**). I'm guessing this based on the 'Monster Movie' episode and the shapeshifter referencing 'normal' parents.

**This would add an interesting element to Adam saying he was hungry when he sat down at the diner.

Editing to add: Like I said, had to visit the bathroom, and after posting this, I read the above responses. {g}