Neither Haener nor Rattler have face a team playing all of their best defense players and game planning their defense to do their best to confuse and harass the QB.
There's a reason a lot of QB's, especially backup QB's, look great in preseason games and not so great in regular season games.
Neither Haener nor Rattler have proven anything about how they would do against a starting defense that has game planned. That's why coaches don't make their decisions just on the performance outcomes during preseason.