I don't really see why this is a deal. If I decide I want to delete the content I put on Medium I very well want them to delete it everywhere else as well.
One could read that as "Medium tries to protect their users content".
Completely agree with your comment, not sure why you're being downvoted. A blog is the same thing as a facebook account, would you like it if you couldn't delete your pictures on facebook?
A blog is not like a Facebook post. It's more like writing an essay, publishing it in a book, and then asking libraries to burn their copy of the book.
One could read that as "Medium tries to protect their users content".