The black part is not soft and they seem to grow so I don't think they are rotting.
The corking thing was just a bad joke reacting to the comment above. But these are cayenne peppers not jalapenos so still, no corking should be happening. Same thing regarding changing color to black while ripening. I know that's the case with jalapenos but I'm pretty sure that's not happening in my case.
We had some very intense sunny days when these started developing peppers, they may be sun scorched. Thanks for the article, I'm growing cayenne peppers for the first time this year so it was an interesting read.