Am I in the minority in that I found the function of the "x" to be very clear? I don't know if it is fair to call it "nothing less than a dark pattern" without a bit more data.
My current feature request is to link the "publisher domain" to the origin article, so that one can always click that to get there and use it to copy the link.
I've also sometimes been on a non AMP version, and Chrome has suggested "a version optimized for mobile". Clicking that has opened the AMP version and after reading the article, clicking the X took me back to the non AMP version.