There's much truth in what you've written, but that said, Earl certainly has shown that he has the temperament for one pocket, a game that I'd suggest can be an even greater test of patience than straight pool (I recall a DCC one pocket match in which Darren Appleton went over two hours without a single good offensive look at the table). Few recall that Earl would have been the Derby City 1-pocket champion in 2010 if not for a terrible match-deciding roll in the double hill rack of the final against Scott Frost. On the other hand, one fact that would seem to support your view is that Earl very rarely won double elimination nine ball events in which he took an early loss. This does, perhaps, bring his stamina and ability to grind in question to a point.
Maybe you're right.