there are many variables that could make up what's needed to build muscle on ones frame,genetics in the end is what dictates the end result.
you could have say for example 5'7 stage ready bber as a lightweight,middle,lightheavy,heavyweight they are all doing same things offseason eating,offseason/pre contest drugs,and all started with same goal get big and along the way each guy got bigger and others stayed with what there bodies could do.a lightweight could bulk to 200 lbs and still end up dried 154 in the end it is what it is..some guys like dex started as bantam and grew and grew some don't.