How to ungroup compilations on iPhone Music?
fingaz's answer is not quite correct—they are talking about when you uncheck the "compilation" box in the Get Info window in iTunes, not turning off "Group Compilations".

The short answer is no, at least not at this time. If you want them to not be grouped as a separate "artist", you would need to alter the metadata in iTunes such that they aren't compilations any more. If this is a feature you would like to see in the Music app, you can tell Apple yourself on this page.