There are plenty of other types of SKS' too from Romanians, Albanians, Yugoslavian and a whole host of other countries that used them.
The only Chinese SKS' without bayonets that came into the country that way were ones imported between 1990 and 1993, after Bush banned military like features on imported firearms which just happened to include bayonets. So when they were removed they were legal again. Other features of course include high capacity removable magazines, folding stocks, distinct trigger handles, night sights, grenade launchers a whole list of other stuff, since they belonged to the whole must ban every firearm without a clear sporting purpose way of thinking.