[wlesieutre]

This sort of thing is actually pretty common in games; you end up doing some engine customization to fit your needs, and eventually you have to say "We've diverged too far to try and keep following the main updates anymore," and you stick with a customized version of an old release.

Nearly every AAA game is going to fit into that pattern, it's just that the 64 bit coordinates overhaul in Star Citizen is probably a larger and lower level architectural change than what most things bother with.