But rail edges should have 4 vertical rows only and there is a lot more in your example. You have not visible control points over surfaces so it`s not visible that surface edges are 4 CP only.

I had it a bit different on my printscreens because I`ve set rails and profiles as inverted to your example but it is not changing anything in that example. Because in MoI profiles are always as low as the edge/curve count is and rail rows are much more dense. Why this happens?

Rhino sweep (6 horizontal rows * 4 vertical rows):


MoI sweep (only profile rows are ok and rail row are denser):


Is this intentional or is it a bug?