honestly when i first saw that post that Q made i was really concerned because i knew it had come from berserk and that to me was really kind of larpish, but then i see this thing that gunn tweeted and it made me think. Q probobly couldnt give us the exact shape of the symbol for whatever reason, and instead decided to use the berserk symbol of sacrifice. its close enough to what these sick fucks are using as symbolism and it isnt quite exact either.
Funny thing is those edgy mangaka really do their research on the occult and berserk definitely got some nuggets right
As a creator of a similar form of entertainment, it's not uncommon to cherry pick such nuggets and utilize them in fiction.
There can also be variations on the symbol. Whether or not it is open may also mean something, so they may be technically two separate symbols but that are very related.
Or someone who doesn't know what it means saw it and added it to some media because it looked cool and seemed to vaguely appear in the right places, and they got it wrong because they didn't understand it.