There is a difference between finishing off an opponent that you have just taken down with a follow up strike and the ground and pound you see in MMA fights. With ground and pound you are basically raining down blows until either; the ref stops you, your opponent taps; you get tired, your opponent stops fighting back and you declare victory and stop etc.
Don't forget that finishing off your opponent (achieving a knockout) is also a very real possibility with ground and pound.
Your attempt to redefine GnP to pounding someone after you have taken their back really shows desperate your cause is on this one.
This is moving goalposts. I am calling you on it.
Just tap. It is useless to deny that Karate has ground and pound. Not only did I give you kata. And then demonstrated videos. And now fights both traditional and MMA.
I think you may have made a typo here. Ground-and-pound is not typically applied when you take someone's back (although it can be).
RTKDCMB has it right on this one. The traditional karate approach of taking an opponent down and immediately adding a finishing strike from standing (or possibly kneeling on one knee) is pretty different from the MMA paradigm of going to the ground on top of your opponent looking to control their position while landing an ongoing barrage of strikes.
You can apply the G-n-P moniker to the traditional karate approach if you like, but I think it just confuses things. The approaches are different and the name originated in MMA and was not traditionally used in any Karate system that I'm aware of.