I find references to "SW edge" ('SW' being 'smooth wall') in USG literature. Ex (link),
SHEETROCK Brand Gypsum Panels, SW Have an exclusive tapered rounded edge design to help minimize ridging or beading and other joint imperfections. This edge produces a much stronger joint than regular tapered edge when pre-filled with DURABOND setting type compound and finished with joint treatment. Except for the rounded edge, panels are tapered like, and otherwise identical to, regular tapered-edge gypsum panels.
I got curious because the USG Gypsum Construction Handbook ch 5, "Joint Treatment for Drywall Construction" says, (bold added)
Prefilling Joints is desirable when there are large gaps between panels. This step is necessary with SW edge board.
Fill the “V” groove between Sheetrock brand gypsum panels, SW (see diagram), with joint compound such as Sheetrock brand setting-type (Durabond 45 or 90) or lightweight setting-type (Easy Sand 45 or 90). ...
However, I don't find (or don't understand) any references to "SW" in what I think is the USG panel products list. Everything there seems to be either 'tapered' or 'square' edged.
This makes me wonder whether 'SW Edge' is a product per se, or just the name USG uses for all its tapered edges.
... And, if the latter, is it necessary (per the Handbook, above) to pre-fill the taper with Durabond/EasySand.