Consider a number line:
┼─┼─┼─┼─┼─┼─┼─┼─┼─┼
... 0 1 2 3 4 5 6 7 8 9 ...
Any point on the line can be described by a single coordinate, so the line is one-dimensional.
We could also describe all of them in terms of a two-dimensional plane [(0,0), (0,1), (0,2) etc.] but that would just be redundant. Just like representing the number line with a taller figure doesn't really make the abstract line any different:
│ │ │ │ │ │ │ │ │ │
┼─┼─┼─┼─┼─┼─┼─┼─┼─┼
│ │ │ │ │ │ │ │ │ │
... 0 1 2 3 4 5 6 7 8 9 ...
So for a single-pixel wide view of SMB from first person perspective, we could consider it a degenerate case of a 2D view if we indexed them (0,1), (0,2), (0,3)... but that would be redundant as they're sensibly just 0, 1, 2...
Consider that any 2D image you see on your screen is just a single-pixel deep 3D image and a single-pixel 4D-protruding 4D image and so on.