-- "I say it is 95% true" This doesn't make sense, something is either true or it isn't.
-- A thought experiment isn't a statistic.
-- Number of years played is only loosely related to an obsession.
-- Playing "for fun and ending up mastering it" is definitely not an obsession.
-- The method you describe is not the method people become GMs in the first place.
-- You don't compare other methods people use to become GMs, so your last sentence has nothing to do with the sentences that came before it.
Truse, I say it is 95% percent true, because what if u started chess "for fun" when u where 5 years old and when ur 65 years old(60 years of playing chess for fun and ending up mastering it!)... so u can play chess for 60 years for fun without studying at all and become a GM, it is almost impossible to be a GM without being obessed!