I'm not sure, it uses your own domain, thus www.google-analytics.com becomes yourdomain.com/analytics.js. Not all requests are proxied, only the ones blocked by adblockers.
Taking this further, you could have your server send an event to GA when /index.html is requested, this can even be from tail -f access_log. No one will know GA was requested.
Taking this further, you could have your server send an event to GA when /index.html is requested, this can even be from tail -f access_log. No one will know GA was requested.