I definitely agree with you here, the first 2 nano-seconds of the article says to use the language header. I thought everyone already did that! :) Even if that metric isn't perfect, I don't know any browser that doesn't let you change that. Further, if it's a user preference to quickly see a website in a different language, get this extension:
https://chrome.google.com/webstore/detail/quick-language-swi...