It was a joke based on the stereotype of singers and their ego. There are plenty of other stereotypes about instrumentalists, such as bass players being simple, lead guitarrist that find everything else support for solos, drummers being brutes, keyboardists being music theorists and so on. I thought you'd recognize it but alas.
But sure. You're using hypotheticals for arguments that you think is proof when presented with historical evidence that the frontman was one job of the band and not the entire act. There isn't really much to discuss against something like that. I could invent my own alternative history too. But why.
And it's not very nice to call the rest of the musicians in the band irrelevant and replaceable.
Edit: clarifications