> Lots of songs have, like, "forced" slang or even changes in pronunciation or syllable stress to meet the constraints of the lyrics.

I agree. I’d be wary of this as a beginner, but when you get more advanced, it becomes helpful in untangling your hearing from the isolated, intentionally clean and slowed-down setting of a class.

People don’t actually talk like that. Some slur their speech, others have a heavy accent, and others just place emphasis wherever they feel like it. Some kinds of music* work well for giving you an ear for the changes that matter (And even with all the changes, natives still are able to understand most music, so it is a skill to learn).

* I love me some guturals in my music, but it's probably not the best way to train your ear for every day conversation