it'd be insulting if it didn't, frankly. i don't know why (or even if) that was ever a real concern. if the homepod couldn't play non-itunes-or-apple-music music it should've been jettisoned into the sun and never released to the public.
i think that article is actually pretty bad - it just says what should've been obvious (airplay Just Works, apple music Just Works), doesn't have answers for pretty much anything else (does itunes match work? does bluetooth work? shrug), and one answer is just flat-out nonsense ("you can stream FLAC from other devices" doesn't really answer "why does homepod support FLAC" when it's not clear what those other devices are supposed to be, because neither iTunes nor the iOS music app provide any mechanism to put FLAC in them, so... what, are you expected to airplay from Vox or something)
yeah i really loved when she wrote an article telling me and others that
we are wrong and apple music didn't delete music files off my macwithout me telling it to and i'm just a dumb idiot who doesn't understand how apple music works and it's definitely not possible that apple music at launch was a horrid pile of garbage that fucked up my library in a hundred different ways to the point i had to cancel the service and restore my whole itunes library from time machine to fix it, on top of all the other defensive-fanboy-tier nonsense imore regularly publishes
(i do not like imore very much)