That's not what happened or what HGH does...you don't just get hench from taking PEDs unless you're training to get massive, which he wouldn't have been. He stopped when he was 14. Never said he wouldn't still have been a great player but when you look at all these great players, Neymar, Rooney, Ronaldinho who are the level below Messi, they were all exceptional as kids, scoring like 10 goals a game and just dominating, that's not unique to Messi at all.
Point being, I wonder if after some time and more understanding people will be able to prove (or disprove) it gave him a competitive advantage, going through puberty on a doping programme.