i was having this conversation with my sister recently, who solely listens to korean and japanese pop music, but doesn't know any of the words and can't sing along.
i found this very strange; i personally can't not know the (perceptible) words to songs i really like, even if it's in another language. it takes a lyrics page online and a few extra listens to pick up the words but it's fine
i know the words to these well for example, despite them being in congolese and finnish respectively:
(staff benda bilili - moto moindo)
(tenhi - vastakaiun)
i did know a guy though who failed gcse german, but could sing along to any rammstein song