I was trying to make a pack to increase the height limit of the end, upon doing so I noticed that the end was not generating the portal nor spawning the dragon. I went through a lot of trial and error, until I tested literally making a pack that only replaced "the_end" dimension type with it being completely unedited and like how it is in the vanilla worldgen pack, and it still didn't spawn, leading me to believe it is some sort of bug.

I have linked the pack below in case anyone wants to check it.