I thought arm length isn't nearly as important at C or G since you're generally playing in a phone booth with OT arm length being more important because of having rushers that can just go around the edge?
That's my understanding. The roughly 34" they look for at OT drops about an inch for OG, and another inch for C. At least that's my opinion, basing it on the arm lengths of current NFL players and looking at their level of play.