Yes, this was speculated in one of the many threads about it, that it might be missing some kind of composition metadata property. However:
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I have reported cases where all tracks are identified as a composition in one version of the album but not another.
Missing composition property: Cat Power Sings Dylan: The 1966 Royal Albert Hall Concert. Example for a very common problem -
Anything with a composer is by definition a composition. Whatever the missing online metadata is. Roon should respect if I tell it that a track is a recording of a particular composition.