correct. the game is finished, as in, both routes end, and yes the routes differ.
now, as the devs wanted to have some kind of epilogue already during rather early stages of the development, Marty (the artist) is still adding to that, well that's extras, yes.
now him being what i call completionist, he's additionally going over some things he thinks need some 'touching up' while working out epilogue stuff, so he's going over old coding, probly improves something this and that, and i bet he'll do for some time until one day for him it all looks right.
that's gonna be a while, likely it'll be longer than just completing the slave route epilogue. artists are strange people.