BYU and Utah don't go head to head that much, and when they do, then filter out things like guys who were always Utah-bound, and always BYU bound. Then you have Utah's proven track record to put guys in the pros at positions like OL, DL, DB. That matters much more than what Utah's record looks like. Their P5 status and pro development does far more.
I've never liked the argument that a negative for an outside thing, is automatically a positive for another. That's not how it works. It's not "better" for BYU. It just might, maybe, in the tiniest way not hurt BYU. Not only is the argument unsupported, it would be stupid sad if true.