The thing is that they'd be potentially giving up clean looks from 3, especially when the Warriors run the PnR with Curry and Green and Mozgov can't quite get out to blitz and recover like Tristan. There could be breakdowns on the floor with Mozgov that gives someone too much room for a 3. I get why they're leaving Thompson out there, he's a better team defender, especially against small lineups.
Go back and watch the end of the 1st half. Warriors went small and Cleveland left Mozgov out there. They put him on Iguadola and jumped the pick when AI set it. Iggy got a few looks, but he's one of their worse 3pt shooters. More importantly Mozgov was able to contest and alter shots at the rim. On offense they attacked Green in the paint (remember he had 4 fouls in the 4th).
Thompson is really not that great when he switches, especially if Steph is smart and takes it to the rim where there is nobody to defend the paint, which is what he did down the stretch.



