thicker sprocket nut worth a check

[Kenbob]

The mechanic that does the work on my bikes said to me about the sprocket nut issue on my 600, Yamaha may have brought out a bigger sprocket nut but not everybody knows how to fit sprockets nuts properly.
I have a 2002 600 and it has the thinner  nut still on it, I have faith in my mechanics ability to fit the nut correctly after He fitted a new chain and sprockets and I'm quite sure he wouldn't allow me to ride the bike knowing the he was the last person to refit it.
I guess it's yamahas way of saying hey guys we've addressed the issue with a bigger nut but if you can't fit it then that's your problem.