Of course he would have gotten an A. The difference between being good and bad at math is whether you need to "spent all waking hours talking about calculus" to get an A.

Extrapolating from 1 course is silly. I worked like a demon to do mediocre (low Bs) in both calc 1 and physics 1, but somewhere towards the end of my freshman year of college something fell into place for me. By my first year of grad school I was breezing through quantum field theory and math methods for string theory courses with minimal effort.