If more bodybuilders were aware of "CNSF" instead of the all talked about DOMS, there would be less guess work when designing a bodybuilding program. CNSF stands for Central Nervous System Fatigue. The lower the reps and higher the load, the more stress is placed on one's CNS. Even when the reps are in mid range (8-12 say), but done with an off the wall intensity rather than leaving a rep or so in the tank, would also lead one to regressing instead of progressing. Why? Read on...
With so many bodybuilders not getting their money's worth for the effort they put in in the gym, it's time to focus on the manner of performing the reps in order to minimise on damage and maximize on overall recovery. Again and to reiterate, to over do it in the gym, and then to add to that damage by under-recovering (in all its facets), would be to seriously undermine one's overall progress, be it in strength or muscle gains.
So yes, simply put, it very much does matter how many reps one does in the gym.