Hi,
I just applied to the program for this year and just came back from it's admitted students day.
Personally, I have very little formal experience in math and computer science, and there does seem to be an emphasis on making sure that everyone gains those skills (however there were also people there who had mostly a computer science background but wanted to gain a stronger foundation in social science theory). As a matter of fact, I think the director mentioned that the entire first year is dedicated to making sure that everyone becomes a "citizen of computer science" and that the following year we would learn more about social science theory specific to our interests and work on our research.
I'm actually between this program and the QMSS MA at Columbia. However, a big draw to this program is that they're aiming for a cohort of around 15 (which I feel like is pretty small for a Masters program) and that they put a huge emphasis on making sure that we produce a meaningful research project at the end of our second year. While they mentioned that they want to produce a new generation of social scientists with programming skills, they also mentioned that they encourage students to pursue opportunities in the private sector as well.
In terms of having a lot of Bachelor's level classes for the 1st year, I got the feeling it was really just to make sure we gained the computational skills and that the undergrad format is the best way to do so (I don't think adopting a grad student seminar format would be useful in learning how to code). I think one of the faculty also mentioned that the students in MACSS would all be in the same section (although I could be wrong)