Unfortunately for the natural bodybuilder, steroids have really fogged up the glasses Steve. Working the muscle much more and giving it more recovery, does not take into consideration the recovery of your other much more important factor to recovering overall, and that's your nervous system. So a natural bodybuilder working his muscles really hard (because he can, due to the 5-day split), still needs to take into consideration the how is he working that muscle (despite it being [say] one muscle vs. a whole body workout). If he is using low repetitions, then that would have a totally different effect and ramification on his ability to recover from such a workout. If on the other hand he's using higher repetitions, with emphasis on metabolically stressing the muscle fibers over CNS stressing his whole nervous system, then not only would his ability to recover be enhanced, but his body's release of Myostatin would be suppressed (which is a good thing if muscle growth is his goal). Heavy loads have been shown to increase Myostatin, aka GDF-8. Do your research on Myostatin, for me I'm content with the metabolic stress type of workouts over the heavy load ones.
It's good to look at the overall picture and take more than one aspect to training into consideration when/before deciding on writing a potentially good metabolic stress and /or muscle (joint) overload program. As I've written before, there's no such thing as a muscle hypertrophy/bodybuilding program, as muscle growth is only a side effect of those two training methods I just mentioned.