Looking at this release, you can see the editor has named the media using the idea of “disc”
I can’t find anything in style guidelines about it, but it seems wrong/redundant to me; the medium type and sequence already do this.It is true that the disc actually says “Disc 1: Studio”, but isn’t this similar to parenthetical annotations of tracks and the like, that mb follows its style, not a direct copy/paste? Can I get a Definitive Judgment?
Funnily enough, this is a guideline since a couple weeks ago 
That said, “Studio” and “Live” would be reasonably interpretable as disc titles, and I’d leave them there if printed on the discs. Just not with “disc x”
What timing! 
For the record, I looked at this and this from “medium title” search, and did not get to that page… so thank you for the Definitive Judgment (DJ).
(And yes, I was going to fix “(studio)”, not remove, so seemed like a good time to ask the question.)
For completeness: https://musicbrainz.org/edit/51641176