For those who are machmir for CY, the exemption for powdered milk is no longer relevant (according to those who ever held of it which was NOT the majority of Litvishe Poskim). The exception for powdered milk and butter is based on the assumption that these products can not be made from non-Kosher milk, which is no longer true with today’s modern food manufacturing technology. There was never a heter for cheese, as someone previously confused cheese with butter. Cheese is actually much stricter as according to many Poskim there is a special issur of gevinas akum and the rennet must also be physically added by a a Jew.
