The "una cuм" is not an audible part of Mass. The priest might not even tell his stance on the "Una cuм" part of Mass. And why does it need to be an either/or scenario. What if the priest is conflicted and says, "Hell, I don't know if Francis is pope or not." Oftentimes is takes humility to say "I do not know." And the simple fact is, apart from a certain, divine, private revelation, no one knows certainly.