Definitely not traditional, as traditional is reserved for meads that are honey, water, yeast (and optional nutrients) ONLY. The only point of contention might be whether it goes into category 26A (Metheglin) or 26C (Open Category). If cacao/cocoa/chocolate is the only additional ingredient, then 26A would be appropriate. Although chocolate is not universally regarded as an herb or spice, there is precedent for considering it as such in a mead, since chocolate adjuncts in beer would generally place the beer in BJCP Category 21 (Spice, Herb, Vegetable Beer), and the full guideline description of 26A says that chocolate is permitted. If there are other ingredients (besides the chocolate and honey) that influence the flavor profile in a noticeable way, then Category 26C is the appropriate place.
Bottom line is that any "weirdomel" that doesn't seem to fit completely into one of the other mead categories, should go in the Open Mead category.