I have the same thing and it drives me mad. It should be a simple business to just carry over the metadata to my phone when transferring files, but it would appear not.
Also very annoyed when the Music app assigns random artwork to a compilation album based on the presence of an artist: eg an 80s comp that has a single track by, say, Bananarama, will have all the tracks assigned the 'Greatest Hits Of Bananarama' artwork.
We're nearly 25 years down the line on iTunes, and we still get bugs like this?