I think the ban is dumb, but: It would follow logically for many that an assault weapon (term from politics/legislation) that is also a rifle be called an assault rifle (even if it is not select fire.) Add that to people not knowing that AR is a reference to ArmaLite and it’s a completely understandable usage. It also turns out that the most vigilant about correcting these usages are often advocates for extremely limited gun control. As such, their primary goal is not simply enforcing prescriptive use of language.