Not for me. Sitting vertical is sitting vertical no matter the length of the stirrup; at least within a normal range. Really short stirrups might force you lean forward. For me, if my stirrups are too long I may be more likely to lean back too far, riding too much off my tail bone.
I clued into the leaning in part because this is probably my number one sin. I get all leaned over, as if I am trying to "help" the horse. But, for the horse to step under himself, thus keep a bend in his body on a circle, he has to be not overly weighted on his inside hip. So, if you lean to the inside, you shorten his ability to reach under himself. IN a tight turn, think of almost lifting up your inside hip to give him more room to get his leg and hip under himself for the turn. And stay perfectly vertical.