Typical GM Speak for this time of year... Never reveal anything about what you are planning to do... Notice that he also says in the article that the Bills don't have alot of holes that need to be filled? So when he says BPA is he really saying "take the BPA no matter what position he plays? Or is he saying "I want the best QB I can get"? One can interpret this in different ways...
And I wouldn't automatically exclude Darnold from the conversation either. Until he is officially "off the board" one cannot assume anything.
But to play along, assuming Darnold is drafted ahead of us and the rest of the QB's are still available at the Bills pick (whenever that might turn out to be) I think my order of preference (if I were McBeane) would be Rosen, Allen, Mayfield...