I mean, it’s not a newly discovered or unstudied condition. And not even that rare in the grand scheme of neurological conditions (not to say it isn’t rare, but it’s not like a 1 in a million thing). There are thousands of documented cases, and while some can get pretty wild, a case where a person turns into something like "the Beast", a crazy cannibal with super powers (or near enough), would certainly be an extreme outlier, if it’s ever happened at all. But that’s why the movie is fun; it takes a real condition and combines it with an absolute human extreme.
Of course. You don’t need to convince me of the movie’s premise. I know and like it quite a bit, even wish we’d gotten more of it. You’ve honestly made me want to go back and rewatch.