Didn't, a few years back, we determine that these were indeed oddly built using pinned barrels inside a threaded sleeve? It seems like they may have used NOS parts and built them for somebody's market...and they ended up in Canada?
I could be completely insane...but I could swear I remember that.
I swapped another D for the one I have now, that one had he bayonet lug ground off and a crappy soft wood stock when I originally got it. It was dumped in Canada when the US stopped allowing firearm imports from China. The one in the pictures has a bolt carrier with a stripper clip guide and was definitely made for another rifle, the one I had previously did not have one.