I mean, I would think this would just be using a larger font size for their bitmap, no?
Apple's terminal doesn't seem to use a specific bitmap codepath - it renders the characters at a doubled size for DECDHL and it looks like it stretches the geometry of the font horizontally for DECDWL.
To be fair, they have one of the very few terminal apps that support double-width/height characters and that passes the VT torture test with flying colors.