I think it is because he relies on spin for his four seam and he would likely lose some of that with the two seam. Also I suspect he doesn't have the command for it (two seam) vs four seam.
It's possible that Max told Schneider he wants to get at least 90-100 pitches in tonight. He's been known to tell his managers how long he wants to go. Allstar break coming up so his last start for the next week and a bit.