2nd half possessions lasted 3 and 4 plays and resulted in punts. The reason to think the backup might have been able to do better is that Jake was apparently injured, and that's likely why he was throwing balls at guys' feet, or airmailing them or failing to execute a fade so badly that a play designed to be safe ended up in an INT that killed a scoring opportunity. I suspect that one of the healthy guys in our QB room would have been able to execute the offense better than that.
I think that's the whole reason why you carry multiple QBs on your roster. If none of the QBs on the roster had the capacity to be more effective than Jake (who was fine - but not exceptional - when healthy) when he's at 50-75%, that's a massive recruiting and development failure.