They should try this for Duke Nukem 3D.
In addition to that, there’s also teleports used for elevators or water. They move you around then using/jumping in. Multiple elevator transports can move you in impossible ways like getting into an elevator, driving down, only to arrive at other side of the same floor.
So I agree. Might work for some maps, but not in general.
As a player, you could see the extents of a sector when you looked at the automap, because the map became visible sector-by-sector.
The exact rule of the editor / engine was actually even stricter. Not only could a sector not overlap itself, you had to make sure that at no position you could see two sectors that overlapped, or the graphics would glitch. If you wanted overlapping, you had to split sectors just to please the engine, even if floor/ceiling height, lighting, textures etc. were the same.
The engine DID need the "lots of sectors so you don't see two overlapping sectors at once", which came for free with a spiral staircase.
I just made two sectors separately and moved one on top of other.
Just tested it: https://imgur.com/a/uDxMDBp