It's always an interesting discussion. With "hard SF," so the science is grounded in our best current understanding of things. That's sort of one end of the spectrum. At the other is pure fantasy, with overt magic and stuff. But if I took a fantasy story and tweaked it to say that it wasn't magic/wizards, it was aliens using advanced technology, does it become SF? Some people will say yes, because there's a scientific explanation, others will say no, it's still fantasy because it's still being treated as magic that is impossible with what we know today, even if there's lip service being paid to the being an explanation.
That's the heart of the debate about DCC: it's full of magic, but Dinniman says the magic is created by advanced tech that defies all of the things we understand about the laws of physics.