When I was a kid, I played center. I'm left-handed. My coach got me to snap right-handed. There are small differences in how the ball arrives, whether under center or in shotgun. Under center, it's about the ball moving a bit left-to-right or right-to-left as it hits the QB's hands. In shotgun, it's about spin. Small things, sure. But small things can make a difference when you want the center-QB exchange to be "thought-free and automatic."
It's a pretty common coaching viewpoint to want snaps right-handed, whether it's a big deal or not. I'm sure like anything, some coaches care more than others.