If we're going to draw any conclusions about muzzle nuts, I think we should distinguish between milled and stamped rifles.
I can't recall seeing any milled rifles, anywhere, either with an attached bayonet or not, that didn't have a muzzle nut. Has anyone else? Eliminating the muzzle threads seems to have been one of the simplifications made with the adoption of the stamped receiver rifles.
I'd also like to see us distinguish between Chinese military rifles, made for their own use or for export, and the rifles made for the U.S. commercial market. For example, commercial stamped rifles shipped with threaded muzzles, presumably because they could use the same press and pin barrel assemblies on more than one model.