I don't recall a player who came into the program who has not gotten stronger. I would expect the same here. I never used the word small.Adds muscle? Clearly you didn't see pictures of him setting the PIAA 100m record that Two-time World Record Holder Leroy Burrell set 35 years ago in 1985 while running for Penn Wood HS. The kid is completely jacked! Where you're getting that he needs to "add muscle" (i.e., implying he's small) is a complete mystery and entirely untrue.
Nor did I say he needs to add muscle. I mentioned development as in improvement. Perhaps you should slow down a bit and chill out.