While you’re right conceptually, this isn’t what the wording means in terms of consent dialogs. Legitimate interest means they can assume, legitimately, that you have an interest in aspects of the site (by you being there) that require X cookies, basically. Ie their product is providing functionality they can assume you’re interested in just by being there, and they’re “pre approving” the tracking/storage for that functionality.
I concur that it’s rubbish and used almost always in a manner that reeks of illegitimacy.