My first advice to these guys would be to come up with a better name. I know which definition of the word "mundane" they're using, but when a word has more than one definition you need to acknowledge that.
I agree with Live Granades' opinion on this.
But I would take it one step further. I think the people behind the mundane scifi movement utterly misunderstand the purpose of fiction. Jules Verne could be seen as an early model of the "mundane scifi" movement. I don't remember where I got it, but I read that Verne's major complaint about H.G. Wells was that "he just makes things up," whereas Verne tried to use real science and technology.
But far more people read Wells than Verne now, even though we have never had a time machine or alien invaders. I think that's because Wells understood something that Verne doesn't, which is also my motto as a writer: fiction is about people, not things.
Verne wanted to make accurate predictions about things: submarines, baloons, etc. Wells was exploring the depths of human nature by stretching the laws of reality. How else could a British person understand what colonialized people must feel like under their rule than by having alien invaders with posers beyond their own imagining come down? Or understand the ridiculousness of their class system without taking them far into future where the system has been stretched to its logical extreme?
That's not to say that mundane scifi doesn't have a future. If the people who are pushing the movement can start making stories that are better than what anyone else is doing (instead of, say, giving everyone else a pass-fail grade on a bar that means nothing to anyon but themselves), they just might, as they claim "Transform the way you think about scifi."