Very possibly. Also, no candidate wants a more dramatic orator as their understudy.
But the other side would be that the demographic where the Dems have the biggest hill to climb is white men, and Walz gives the white guy in the F150 permission to like a Dem more so than any other possible choice. My take would be that that was the single over riding consideration. And as I mentioned before, don't underestimate the importance what their internal polling may have been telling them. If they were behind in PA, maybe you need Shapiro. If you think you have PA, you make the broader play.