why does everyone want to compare being fluent with being a gm?
look at it THIS way. many millions of people will be fluent in English, Russian or French. but despite intense efforts Almost Nobody becomes a gm. its just the tiniest percentage of chess players-- even as a percentage of those that try as a kid.
I mean obviously age plays a roll, brain works slow I know that , but..
I can compare chess and a new language.
Imagine you want a child to learn a brand new language, send him abroad and he will speak fluently in couple of month.
Send an adult to lean new language he will speak fluently after years.
So my point is in both cases people will speak fluently , but it's just matter of time. So why chess can't be the same I belive anything is possible.
Of course their is some age limitations, 50 + probably stands very slim chance to speak fluently or be a GM but still not impossible, almost impossible to be correct.