I see the logic of it. He's the governor of arguably the most important state of the election. If you think he could help win in Pennsylvania without costing too many votes from the only other 6 states that matter it would be a good pick
I was reading that he would probably hurt the surrounding 6 more than many other options and wasn't that much of a lock for PA itself. Probably not worth the tradeoff. Make several virtual locks and maybe swing PA vs make some of the 6 less sure and still be shaky in PA anyways. PA is important but potentially so much of a tossup that too many eggs in one basket may cost several surprise other places.