It's not bayonets they have a concern about - its a classification thing. All military rifles since the revolutionary era to now had a bayonet attachment. Even the Springfield, the M1, Lee Enfields, some Mausers and carbines too. That is why they also added the 'threaded barrel' thing too almost every modern battle rifle has some sort of muzzle attachment too. This is a ploy to make it hard for manufacturers to just tweak a model type/no. or other features like furniture to get around bans by definition. Lugs or barrel threads go after one of the most expensive parts of a rifle, the barrel.
The politicos are getting incrementally smarter, and trying to disarm via broader strokes.