Also in a Coons patch there is not exactly a "sweep" happening.

It's more like a Loft between the opposite pairs of curves, then those 2 lofts get combined together into a result surface.

There isn't really a sweep happening, it's more like a membrane attaching itself to all the curves.

There isn't one set that is the "profiles" and one set that is the "rails" for this particular kind of surface generation, they are all more being combined equally in a sense.

- Michael