R’ Moshe’s teshuvah was written for the USA, based on US laws. I honestly don’t know how it would apply in Israel. I do know that there are plenty of countries where you can’t rely on it.
R’ Tzvi Pesach Frank zt”l had ruled as Chief Rabbi that powdered milk was ok, but not liquid milk. The Rabbinate is simply following the psak from a former Chief Rabbi. If R’ Metzger would officially pasken that it’s not a problem, maybe they’d change their opinion.