I’m sorry to do this to you. I have been perusing those links. Where does Peters address the connection of perpetual continence with doctrine? As far as I can see this is Canon Law and Canon Law typically deals with discipline (which can change).
Of course, having said that, I also know that Canon Law that addresses the receipt of communion deals with more than “just discipline” (and connected to doctrine). This is why the Church has never allowed non-Catholics to receive communion (that is, before Vatican II and JPII’s 1983 Code).
Keep reading. If Peters does not deal directly with the doctrinal issue, he refers to people who do.
Discipline is always based on doctrine. Discipline that is not necessitated by doctrine is a mere imposition. (And the Church is vigilant not to impose disciplines on the faithful that are not logically necessitated by doctrine.)