I feel that the cornbread or any other Core recipes can be considered Core...as long as whoever is making them pays attention to their hunger guage and doesn't binge.
The Core plan satisfies you because it is really hard to go on an "apple binge" and eat 7 of them in one sitting...and I have a hard time seeing anyone sitting in front of the tv and scarfing 4 salads.
I think as long as you are exercising caution-and making a small batch of whatever said recipe-and eating a small serving of it then you are fine. If you are making a batch of Core muffins and eating the whole dozen because they are all Core ingredients-then you are missing the point.
It is no different than an Atkin's dieter scarfing an entire pound of bacon or drowning their veggies in butter because there are no carbs in it...or a fat gram counter eating an entire pint of ice cream themselves just because it is fat free. You can have indulgences and use these recipes within reason...but no matter what plan you are on-don't dance around the rules just to find a "legal" way on your plan to be a pig.
Just my 2 cents...
Aphil