Terrible logicage excuse, its dumb. If you're trained and groomed by madara uchiha and enhanced wit Hashirama cells and possess a deadly Mangekyou, then age doesnt matter. Same way a 16 yr old naruto and sssukes age dont matter when they solo most.
1. Adult Naruto & Sasuke (Hagoromo chakra) > the younger selfs in every catogory reaction speed power etc.
Same for Obito training with a Madara who could not walk or do anything but talk is not training at all and that still does not mean his reaction would not improve. As if you could max out your potential at 16 to began with post is all types of dumb
OT - Team Tobirama wins like i said