Eliminate unnecessary area loading in PoE 2

From what I know about the Unity engine, simply adding building interiors to the same 'level' as their parent zone would mean you could just teleport players in instead of loading a new area. This would mean that you wouldn't have to sit through a loading screen just to enter a random peasant's house. It would also allow you to venture into buildings without 'gathering your party' first.

Obviously, nothing would change for dungeons or large dungeon-sized buildings. I don't know why they wouldn't have done it like this to start with (I can't imagine memory being a concern since interiors tend to be small). Perhaps someone with more Unity experience could explain.