There seems to be tension between using the spine and Label Guidelines.
Labels in MusicBrainz refer mainly to imprints.
An imprint is (strictly, and nothing more than) a brand (and trademark) associated with the marketing of sound recordings (an imprint is not a company). … Imprints are the information you certainly want to add in the database and is the information available on sleeves in the form of a label logo (a.k.a. imprint). Imprints are labels, as one usually understand it. Specifically, you should favor using names as they are represented on the imprint, rather than using a company name (usually found in “copyright”/“produced” mentions).
Would appreciate more discussion.