They appear to have each section of the map available as a PDF. I guess everyone just does it a little different. I'd expect NYC to be closer to Boston though since they're from the same era and both have limited area to spread and have a lot of grandfathered in buildings.
I'm a bit surprised DC is so segmented by land use, though I suppose it's a more recent city it's not as if 200 years is chump change. It seems like the zones are created and existing stuff gets exceptions carved out, and if they get torn down then they lose those exceptions and become the default type. So if buildings get destroyed quickly or if there's a lot of space for new construction I'd expect more simple separations between land use types.