I didn't know but it seems that PHP is replacing dots by underscores in parameter names in all global variables ($_GET, $_POST, ...). This bug in PHP is described on stackoverflow and on php.net.
Since the Request class uses those globals in createFromGlobals method, all values in Request::$query, Request::$attributes, ... are "wrong".

Is this a known and accepted behavior ? There is a Gist with a proposed solution. Do you think it is worth a PR or do I have to wait for @fabpot's one on RequestFactory (#8957) ?