Collins planned to redshirt Yates either way. Obviously, that's how it's played out, but I'm not talking hindsight. Lucas Johnson was coming back. In the worst case scenario that you're suggesting, we'd need both Graham and Johnson to go down permanently in the very next game in order for the redshirt to come into play.
To use the same logic you're presenting, they could run with Oliver one game or part of a game if necessary to preserve Yates redshirt in the doomsday scenario you offered. That doomsday hypothesis you're presenting seems so unlikely to me, which is why I'm not into blaming Collins on this one. To call this choking under pressure is almost exactly the opposite, imo. They followed the gameplan to win a game, one that would have been predetermined, and did not waver from it due to circumstance.
They knew they had a backstop of 3 more games to play him, which is only happening if convenient. Yates wasn't and isn't playing 4 meaningful games. He may not play a single meaningful game.