I understand why you say that, lorangrecords, but the real world doesn't always neatly fit into whatever "rules" sites such as this and Discogs might come up with! When MCA bought ABC, they acquired unknown (to me) quantities of complete album packages, covers without pressings, and pressings without covers, to be rebranded and renumbered as MCA Records, many of those very inelegantly accomplished by stamping the new catalogue numbers on the front covers, as in this case. Some of the releases in this series (as well as the MCA Impulse! MCA-29000 series) included inserts of all the relevant releases, making it clear that the intended label was MCA or MCA Impulse!, and those that continued selling after the old covers and pressings were used up were re-pressed with MCA logos and labels, and the MCA catalogue numbers everywhere. So, MCA very much needs to be at least the second label and catalogue number on this, but I think making it the primary label and number more accurately reflects their intent.
I've added MCA-28034 as the second catalogue number. A great group, but unfortunately MCA didn't reissue their three pre-ABC albums. I wonder if this is because they didn't have any paperwork proving ownership, which seems to be a common problem with Duke-Peacock masters. One early 60's Dixie Hummingbirds album, IN THE MORNING, also wasn't reissued by MCA, whereas all their others (some of the later ones markedly inferior) were.