Most people that know nothing about rifles probably think any semi automatic rifle with a pistol grip and a magazine capable of holding more than 5 rounds is an "assault weapon" as their knowledge probably comes from war movies.
Personally, if I lived in the US, where home invasions by multiple gangsters occurs, I'd want a weapon with as many rounds as possible, given it takes a lot of bullets to actually take down moving targets.
IMO it's just Biden pandering to his base, as he must know a "ban" is unlikely, and that all a "ban" would do is take them off law abiding people- the bad guys can get all the weapons they want.