It's more so really smart development. The geometry is mostly pre-computed. The only time it would have to do runtime computations is for maps where there's multiple floor planes of different height level.
Duke Nukem 3D's renderer is sector based, not BSP based.
There's a lot of room-over-room stuff going on that a BSP system like Doom's couldn't represent.
You may have noticed that Doom has a lot less verticality.
Yes, there's staircases and platforms but you cannot willy nilly stack floor planes on top of each other.
Given BSP is still a struggle, I don't see a sector based renderer ever happening on Genesis.