That's a good point, you're correct, "D-Day" was the designation for the day in the plan, as H-Hour was the designated hour of execution (with plus and minus designations for days/hours after and before the target date/hour).
On the other hand, "D-Day" has a certain connotation in the broader sense, identifying with the Normandy invasion. That is to say, that many people, outside our hobby but also within, probably think "Normandy, June 6, 1944", when they hear "D-Day", so it's perhaps imprecise, if K&C meant another operation.
It reminds me of a controversy last month about the October issue of "FineScale Modeler", that featured an article on a build of Trumpeter's 1/32 TBF, finished as "a Midway Avenger". The model was finished in relatively pristine condition, with markings that included the meatballs and rudder stripes that US Navy aircraft carried in the first months of 1942. Those markings were painted out by the day of the battle, and we had the same kind of discussion--when you hear "Midway," what do you think of? Do you think of an aircraft of a type used in the battle, but as it appeared several months before, when it was delivered to the Navy? Or do you think of the famous photo of Ensign Earnest's TBF, the only surviving aircraft of Torpedo 8, on the ramp at Midway? There were those who took the first line, but by that token, you could build a model of the Yorktown as she appeared at launch, and call it a "Midway carrier".
But having said all that, it sounds like they goofed it up.
Prost!
Brad