That's not true at all. Different QB's have different habits. Throw speed, accuracy, tendency on ball placement. Even down to the wire on the reciever anticipating what the QB will do if they get pressured. All of it is different and plays a significant role to the WR to succeed.
I don't see any all-star WR's on our roster that can adapt to two QB's in a few practices. But trying to adapt to one is certainly putting your receivers in better situation to succeed.
Hopefully this is just talk so that Washington can't gameplan for just 1 QB. Because the QB battle should've already taken place in training camp. He should already know exactly who he's starting when he's walking into the facility Monday Morning.
Anything less is failing to put your players in best position to succeed, and not good coaching.