As far as I know the parser already does it:
static function plural( $parser, $text = '', $arg0 = null, $arg1 = null, $arg2 = null, $arg3 = null, $arg4 = null ) {

		$text = $parser->getFunctionLang()->parseFormattedNumber( $text );
		return $parser->getFunctionLang()->convertPlural( $text, $arg0, $arg1, $arg2, $arg3, $arg4 );

}

So I'm puzzled why the are hacks in the language files at all.

Hacks are removed and parser indeed should normalize the numbers.