The "He doesn't know what he's talking about because MOBAs and MMOs are different!" crowd is kind of...off.
Morello is the lead content designer. A huge part of his job is to have an accurate understanding of why people play his game and how to reinforce the points that his audience cares about. This kind of crap is right up his alley. This is literally what he does for a living.
I don't always agree with Morello but I have a lot of trouble shooting his opinion on this issue down simply on the basis that he doesn't run an MMO. I don't think there's a good way to prove his words right or wrong on this particular issue; but it seems very unfair to dismiss it as nonsense for no good reason.