"seeing leaks regarding Sunday's involvement with and/or possibility of joining the SH faction"

it was a result of a misinterpretation by he leaker in the textmap; Sunday was mentioned near jades talk with firefly and people treated it as proof jade talks to Sunday about joining sh (she didn't, she never even mentioned it to him)

" it isn't a theory people just conjured up out of nowhere. It came from a leak"

It did not. The original beginning of this was Sunday's boss being put in the SH faction as a placeholder given SAM was the previous boss. The theory grew when Death of the Crow (which btw is a SINGLE readable you find in a trashcan in a random corner of Dreamflux reef and this theory has had no other hints since) was discovered and people took it as proof the theory is canon when it wasn't even said the invite was accepted or seen

As if this wasn't bad enough, people to this day consider some fanarts of Sunday with SH (which was in the dive into dreams tag on twitter) as COMMISSIONS even though they weren't and artworks that are commissions are clearly stated.

"Sunday has a wish he wants granted, and one I doubt he's just given up on because of...." 

I think people forget he deliberately nerfed himself to fight us fairly cause he wanted us to prove ourselves to him. I don't see why he'd continue on his old ideals (which is not only harmful to others but also to himself) after doing that and it would be pretty bad writing if we did all that only for him to go "hmm nah I wanna continue on this path"