He was in the PFA Team of the Season as voted by his peers:
That's the one!
I think your takes on Gray are pretty balanced but would answer you like this:
A kid that's played 50 odd games for a team that should have been promoted in the Championship...
Won Young Player of The Year...
and also voted Team of The Year by his peers...
that's not a kid with much to gain from staying at Championship level.
In terms of comparing him with Bissouma. Up until the Everton game I'd say that he's a much better and more varied passer of the ball but have to admit, I really enjoyed seeing Biss spray it around vs Everton. Hopefully, that continues. Once he's acclimatized to the Prem, Gray will use those long legs to win tackles/duels and eat up ground in a way that Biss just can't do but for now, Bissouma is probably the better ball winner at prem level. How long that stays the case will depend on Gray's development and adjustment to playing at this level but it might surprise a good few how quick that will be. His understanding of the game offensively and defensively, like Bergvall, is freakish for an 18-year-old.
I think/hope Gray only needs to be Bissouma's rotation this season and gets most of his starts in Europe/Cups but if Biss does go off the boil, Gray will be right there consistently knocking on the door.