FF12 went through different versions too. started as an online game, they were going to have SD character designs at one point, there were at least four different versions of the character growth/license board system, etc. Most projects that take forever went through changes in design or technical direction, had a lot of work scrapped at some point etc. DNF is same
at any rate, I think the work done for the PS2 version was mostly pre-production. They said they kept the scenario and world from that version but not the gameplay/battle system ideas. I doubt there was much PS2-specific programming or realtime art assets they had to scrap