Core request handler documentation maybe has conflicting information? I wanted to confirm with the community and maybe get some clarity about D8 Documentation:

On the Core request handling system ported to Symfony2 framework page it states: 


  The PHP superglobals for $_GET, $_POST, and $_SERVER are deprecated
  and should not be used, ever.


However, I can't seem to locate this information on php.net. PHP setting register_globals is deprecated. Is this what they are refering to or did I miss something huge in recent news? No longer able to use $_GET in our custom modules for D8?
I'm pretty sure the advice stems from this issue: Replace almost all remaining superglobals ($_GET, $_POST, etc.) with Symfony Request object. The opening gambit from that post is:


  In order to depend on using the Request object to determine caching, we need to ensure that everything uses it, rather than raw PHP variables for $_SERVER, $_REQUEST, $_GET, $_POST. 


I don't the quoted comment is suggesting they're deprecated in PHP as such, just that using them in Drupal isn't going to be reliable.