> Adjustable vocals: Users now have control over a song’s vocal levels. They can sing with the original artist vocals, take the lead, or mix it up on millions of songs in the Apple Music catalog.

Everyone I know would call that karaoke. And I assume will when telling their friends about this new feature.

If I search for Apple Sing on google news, the first 5 articles all call it "karaoke-like" or just "a karaoke feature".

Whatever reason they have for not saying the word karaoke, I don't think it's that it's not what most people consider karaoke.