Not that I would read into these numbers at all, but he's actually been quite good this season with runners on base, and better than with the bases empty.
Empty: 18% K, 11% BB, 1.4 HR/9, 5.44 FIP, 4.50 xFIP (.293 BABIP)
Men on: 22% K, 12% BB, 0.3 HR/9, 3.25 FIP, 3.82 xFIP (.329 BABIP)
This seems like a pretty silly narrative.