This is not a bug, not an oversight. It's an unimplemented feature because of the huge amount of time and effort it would take to implement the ability to:
- Get in/out of your rover anywhere
- Walk from anywhere to a facility
- Enter/leave a facility on foot, despite normally only being able to enter with a rover.
- Walk from a facility back to whatever random place you left your rover
Even if you could do all that, Santorini central doesn't have any fuel cells. So you'd have to also be able to walk from central to the quarry and back. All of which is a moot point because I believe you can make it from Talos to Santorini without going to Laurion, you just need more familiarity with the route. And even if you can, it is in fact faster to drive from Laurion, back to Talos then to Santorini than it is to drive straight from Laurion to Santorini.