yes because he took more drugs and trained more and more..
anyone will add size after starting to take drugs or increase them.. this is not "maturity"..
Because he trained more and more yes , because he took more drugs no. More size doesn't always equate to quality size. and it's not like Frank Zane went from 150-210lbs and you don't even know if he did more drugs , that's just speculation on your behalf
Muscle maturity is an appearance of the muscle , it has to do with quality and how the muscles ti-in together how they look like they've been trained constantly for years on end. and polished complete look. And it doesn't really have anything to do with age because Shawn Ray had great muscle maturity when he first turned pro in his early 20s but he looked like he was a seasoned pro with the level of quality he showed.
Take a look at this photo , Shawn Ray winning the nationals at just 21 , his physique is what they would say shows a lot of ' muscle maturity ' despite the fact he wasn't lifting that long , his physique is high-quality , very polished and complete. Ironically that's the rub with Shawn Ray is he never really improved he won the nationals at 196lbs and competed at 205lbs , he refined his physique a tad more and worked on his posing but he really didn't change.