Yup, everytime I've seen this X button, clicking it has done exactly what I expected. I've also sometimes been on a non AMP version, and Chrome has suggested "

Yup, everytime I've seen this X button, clicking it has done exactly what I expected. 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.