I think this is our district's idea of providing "enrichment" for kids who are already advanced. Instead of explaining one way to add 3+2, they can explain three ways. Then the teacher can pat themself on the back and say that they are offering each student a challenge. At one of the schools I visited, that's what I was told they would do with DS, since "acceleration is harmful" and I said thank you very much and walked right out, never to talk to them again. But it seems to be a common sentiment. That being said, I do think the "fuzzy math" curriculums like teaching this way. They probably think they are teaching to the whole brain or some other nonsense. DS hates all of this explaining as well and I think it's going to hold him back. I asked him today what is 3/4 of 12 and he told me 9, but if I made him explain it would probably be nonsensical (I've never taught him how to do the computations so he couldn't have been doing it that way).
I don't have any feedback on that particular curriculum, never heard of it.
