Smashing Pumpkins is alt rock for me, not Grunge.
Mother Love Bone is Seattle Grunge and started the movement, but it was late 80s and they were not part of my mainstream high school limited attention span. I didn't really know about them until college.
Shannon Hoon has no part of the conversation, though "No Rain" is one of the all time tracks from that era.
I'm standing by my original post.
Actually MLB created the end of the Seattle scene's formation. Wood's death and the demise of MLB gave birth to PJ and Mudhoney. Those two bands basically finalized the roster.
Every other major band involved in the Seattle sound was before MLB with exceptions to Mudhoney (formed at the same time as MLB from the break up of Green River. Mark Arm and Steve Turner left to form Mudhoney while Ament Gossard & Bruce Fairweather left Green River, joined by Malfunkshin's Andrew Wood to form MLB.)
Upon Wood's death, Ament & Gossard recruit Mike McCready, Eddie Vedder and Dave Krusen to form what would become Pearl Jam after starting off as Mookie Blaylock.
So the Melvins, Malfunkshun, Green River, Screaming Trees & Soundgarden were all mid 80's, even Nirvana and Alice N Chains were formed before MLB.
As far as style, MLB still had Wood's glammy hairband feel but Gossard and Ament really grew at this time, maybe from having to synthesize their thrashy Green River sound with Wood's desire to be an edgier version of the standard MTV
Poison rock that was on the way out.