Darnold is also probably going against the 3s (I don't know either team's roster to know for sure). He should look good against them, especially when teams do no game planning for preseason. If he wasn't standing out then there would be a problem.
That being said, hopefully both him and Bridgewater look good in all 4 games. Some teams don't have a backup capable of running an offense so having 3 would be a really good situation for them if someone goes down.