Transpose list.combine but not list.create?

This is the exercise “Exercise - 3D Lists” in 6.4 n-Dimensional Lists of Dynamo Primer.

It says

1.In the previous exercise, we were able to use a List.Transpose to create a ribbed structure. This won’t work here. A transpose should be used on a two-dimensional list, and since we have a three-dimensional list, an operation of “flipping columns and rows” won’t work as easily. Remember, lists are objects, so List.Transpose will flip our lists with out sublists, but won’t flip the nurbs curves one list further down in the hierarchy.

In the later section, it says

2.The function we’ll apply to List.Map is List.Transpose, which will flip the columns and rows of the sublists within our main list.

My question is
The structure and contents of the lists in the list.create and list.combine look like the same, why transpose can by applied on the list.combine but not the list.create?