I know you can add them from any reachable depot. I didn’t know about the nearest stop thing though. It could be my TTD/OpenTTD experience, when you clone a vehicle (first step of replacing) it will go to the first stop on the route list; trying to remain relevant information.
Easy enough to test though.
With road/tram/train types, I’ll create a line with two stops,
the first stop on the list is further away from the depot than the second stop.
I add a vehicle and see which it goes to.
Thanks for making me doubt this presumed fact.