Which they CANNOT do FYI. All of linux is distributed under GPL, and any developers that have distributed their code under it, cannot legally withdraw or revoke their license. They can stop their future contributions from using the GPL, but what is already in there now they granted an irrevocable license to all to use, modify, and distribute it via the GPL.
You know how I know you didn't read the article?
Hint: it's because what you said, and why it is apparently not correct for all code bases and all contributions within some code bases is covered.