Even if a player does win a slam without facing Federer (somehow), everyone is bound to piss all over it - calling it a cake walk draw. So yes, it does seem that you need to beat Feds in order to become a GS champ in reality and on this borad.
Well I've also seen people calling a GS-victory a victory with a '*' attached to it when that winner didn't play Rafa to get there.
Eventually it is all very simple: to win a GS, you'll have to beat all seven opponents in front of you, whoever they are. Not as easy a job as some make it seem to be.