I always thought of Cloud's physical strength as secondary to the displays and progress of his mentality throughout FFVII.
Rather, I believe the story of FFVII to be journey of Cloud's mentality: initially under a false pretence he can maintain a sense of power and influence on the party, followed by a break characterised by physical weakness and coma, before finally going through a sense of healing and reparation which ends on a note of catharsis.
So how strong Cloud is really isn't the point. I see nothing wrong with Cloud having realistic musculature.