again, what happened to the man, the myth, the legend, Brock Osweiler and his winning record as a backup
Your argument is insane and sounds like an argument you make up after your initial position is proven to be nonsense.
The least useful stat of a backup QB is probably his W-L record. It's like trying to judge a relief pitcher based on wins and losses, it says almost nothing. W-L is not as useful for starters as people pretend it is either but at least the entire offense is schemed and built around what a starting QB can do so it does tell you something useful, for backups? Not really.