I am currently on 8.15.25019.13002 for Mac, and it seems like the behavior has changed with respect to selecting subobjects (?).
If I select line segments within polylines and run EdgeSrf, it discards my selection and gives the message “select 2, 3 or 4 open curves”. If I explode the polyline it works as expected. Similarly, if I make a trimmed surface from the polyline (PlanarSrf), and sub-select the edges, that also works.
I do this so often that I don’t really think about it, but I’m fairly sure that until the latest update I could use EdgeSrf with polyline segments. In any case, it seems like it should work.
Or, is this controlled by a setting somewhere?