And looks are the crux of the matter, not function. The Federal Assault Weapons Ban of 1994 banned the Colt AR-15 specifically, but not the Mini-14, because it does not have a collapsing stock, pistol grip, bayonet mount, flash suppressor, or (LOL) grenade launcher.
Put another way, an AR-15 variant was illegal under the ban, and the Ruger Mini-14 was legal, not because of their capabilities, but their ergonomics. The AR-15 looks like a military weapon, therefore illegal. The Mini-14 looks like a hunting rifle, therefore legal.
By contrast, in Canada, the RCMP puts both rifles in the same category: restricted, then as of 2020, prohibited. That's due to Junior Trudeau overreacting to a particular shooting spree, but at least they're consistent and not just going after scary-looking black guns.