Programmer (1 dude) works part-time (like most of the dev team, aside DC). He has to re-write the entire code (cause reasons) while waiting for the posers (3 dudes as of last info) do every scene (not just the lewds) with the new wider backgrounds, using the ~400+ image bits to "composite" all the girls back into not-mutants versions of themselves (no face and 4 arms, etc). All of that part-time, as said above
Bolded italics underlined : the art has been done for most of the year (check the tracker). And it's not "some" art, it's every background being ~1/3 wider, a bunch of new places (trucker bar/forest lodge/bowling alley/etc) with 2-3 variants for time of day + interiors/exteriors. Though all that isn't a bottleneck to the coder and/or posers