This Needs to Be Said

[Granyala]

Yeah, instead of designing one straight line with three circle rooms, they have to design a huge zone with caves, slopes, verticality, etc...

Yes they have to build the map. But, provided a good map editor, that doesn't take nearly as long as creating new art assets.
Yoshida said in an interview that creating 3D art assets is their biggest bottleneck.

In that light, it makes sense why they constantly re-use stuff they already have.