I have entered Chocolate Porters, Coffee Porters and Porters with both Chocolate and Coffee into competition into the Spice, Herb, Vegetable beer category. Specialty beer category is a catch all for beers that do not fit somewhere else. If the beer fits somewhere else, you will get dinged for that, especially a comp such as this.
Also how you list the beer within that category makes a difference. I contacted Gordon Strong about this not too long ago and he helped me take the same beer from a 38 to a 44 in back to back competitions. I understand they where individual comps and all but how you label the beer "paints a picture" for the judges to pick through the beer. The first comp I labeled the beer "Porter with Chocolate and Coffee". Since the judges noted the coffee was more up front and the chocolate came off more like cocoa I took that and put that in the description so that was what they tasted. The next comp I changed up the wording and entered it as "Porter with Coffee and Cocoa" and drove in several more points for it. These comps were literally like 2 weeks apart with the same beer. but I believe the changes made a difference and it made sense to me.