Consider changing getVersionBySelf() in functions.inc.php to use REQUEST_URI instead of PHP_SELF. I want to point all 3.6.x whatsnew to the 3.6 version. The problem is, because we use PHP_SELF it sees where the 3.6 version is located and never says a user is on the latest build. I am working around it by copying the files from 3.6 into 3.6.x. This is less than ideal.
I wrote this bug instead of changing it myself as I am not sure what else relies on the current behavior.
l10n whatsnew pages rely on this function but I don't think your proposed change would impact their logic, we can test that on trunk after 3.6.4 is out I guess.
tested with locales and done in r70217