It's mentioned in the description of The Veil that it updates itself as The World develops. There's even a specific passage about a shade recalling the day when electric lights first appeared.

Interlopers are rare because (again, as mentioned in the text) several Gods work to keep them out. It's a crossroads in the sense that well-prepared Heroes could use it to reach an Underworld they otherwise couldn't, and more importantly, because those who wind up there after they die can choose to leave for another Underworld whenever they want to.

Finally, and I know you're already...