regarding Omnivore Recordings (https://musicbrainz.org/edit/42088305 ), the label was added in late 2011 (https://musicbrainz.org/edit/15665866 )—without any type set until my edit. since then, the original editor who created it and the others thereafter, have all used it as an imprint, for release label use. (while i cannot recall when the imprint sub-type was introduced, i reckon it wasn't as far back as then.)
i do not disagree that Omnivore might be considered a "reissue production" label; they do seem to license a fair bit of catalog recordings from other labels. but, even without considering how it's been used by editors for the most part in the last five years, i think i can safely say that the cat no. prefixes these releases have (eg OVCD/OVLP for CDs & LPs respectively), and their barcodes, lend weight to the argument that Omnivore Recordings is in fact a valid imprint. so i'm not sure why you would insist in your edit note that it "clearly" isn't one.
the other aspect is this: even if Omnivore Recordings might perhaps be characterized as a reissue production label, that fact, while good to know, has relatively less impact and limited use as far as the application of the label in edits. comparatively, whether a label is regarded valid for use as an imprint or not is much more significant to editors, generally speaking. as i've pointed out, from my observations, far more editors add release labels to releases than those who would apply labels to other types of edits (copyrights, manufacturing, etc) involving the subset of labels that typically aren't valid for use as release labels. add to that the fact that any intention to now reclassify Omnivore Recordings as a "reissue production" label is going to upset all these previous edits (since you contend it's not an imprint).