Yeah, I sloppily lumped together the two injury designations. If a player doesn't agree to the injury settlement, he goes to IR.
It's also true that roster depth considerations are a factor in a great many IR decisions. That doesn't necessarily mean "stashing" or "red-shirting," it's just the way the IR system works. For each injury, the team has to decide if it's worth devoting the roster spot to waiting for the player to return. It can be a tough decision, and sometimes you regret the choices later.
Anyway, my basic "stashing" challenge remains: Name a young player on the bubble who, at cutdown day, was sent to IR with a dubious injury, then came back to contribute the next season. Personally, I can't think of one.