I don't believe this is a large enough issue to fork to my own repository to solve it, so I will just submit an issue for it.

I don't want cast doubt on your team's knowledge of your own code, but have you checked the Ender Watcher's TileEntity/BlockEntity class?

It appears to be checking for when a player wears a pumpkin in their head armor slot instead of a carved pumpkin (which is what I believe the correct check behavior of the block is supposed to be). Players can't wear uncarved pumpkins in their head armor slot without using commands (You probably already knew this). I currently cannot check my own install (Quark 3.2-358), as my currently-installed Java version is too new for both my dedicated standalone decompiler and my IDE.

This issue appears to affect all branches of this repository >= 1.14.

No need to be apologetic, things like that slip through the cracks when porting. Thanks for pointing it out.

Oh yeah, nearly forgot to ask: This fix won't be backported to versions older than 1.19, right?

Correct, sorry.

Not to worry! If anything, the fault is mine for not realizing a couple years sooner when we were still on earlier versions of MC.
Oh well.

Incidentally, I really liked the way you implemented the fix. A fake Enderman Entity attached to the BlockEntity to check for ALL theoretically usable Enderman non-aggro masks, past, present and future? Pretty smart stuff, but once you think about it it makes perfect sense to do it like that. I wouldn't've thought of that. I would have just done the obvious fix and changed the helmet item to the correct one, or maybe checked against an item tag.