It's pretty common these days to build "five over one" construction. This is typically a 3-6 floors of wood frame construction (Type 5 in some codes) over 1 or two floors of concrete (Type 1)[1]. It's a cheap way to build mid-rise buildings which would be banned by this proposal.

[1] Sometimes this is explained as the "five over one" meaning five floors of wood over one floor of concrete, rather than a reference to building codes. Either way the concept is the same.