I think that was when Laver, Borg and Sampras were honoring Federer so what would you expect Borg to say? Sampras said the same thing but he took it back and I don't think he ever believed it. I think Sampras thinks Sampras is the GOAT. Laver said the same thing and yet he said later he would love to play Federer with a wood racquet and that he wasn't afraid of anyone with a wood racquet.
Basically I think most of these guys, including Federer believe that they themselves are the best. Nothing wrong with that because that is what drives them to be great.
Nadal always says Federer is the GOAT but you know he feels that he should beat Federer every time they play.