Well, if you listen to many of Irving Berlin's songs, you'll see that although he starts in his favorite key (transposed to whatever the singer needed), he often has bridges or sections in other keys, so it's not like he COULDN'T play any other key... And his songs certainly had some sophisticated changes, so again, he was FAR advanced beyond simple 'one key' mentality.

But it does show that genius, when faced with a challenge, finds some way to cope... So what if he only played in F#, he still wrote some of the world's most enduring standards. And analyze any (or many) of his tunes and you realize that harmonically there is no way you can play them if you are limited to one key. He liked to simply start in F#.....

Now there MAY be the odd genius here at SZ, but personally, I think if you DON'T consider yourself a genius, your efforts might still be better used learning to play in as many keys as you can. If you study long enough, and practice hard enough, you MIGHT eventually almost get as good as old Irving....