Yes, using Amex will avoid DCC. It's the same with Discover (but with more limited international acceptance, of course). JCB and UnionPay also do not have DCC. There is interoperability with Discover in theory but not in practice with JCB and UnionPay.

I read the article, and it's a good article. However, notice that it was a freelance author on behalf of American Express. If I were Amex, I would have reminded the author that American Express cards do not feature DCC (and list that as an advantage of using American Express where accepted internationally).