Yes I agree, apps should never mentioned XEPs. Most devs have no reason to even know about them, why would a user case? Some apps are built by protocol nerds and they like seeing the list. Maybe very hidden is ok but in general not something any user cares about.
How would devs not have to know about them? Say I want to write an XMPP-enabled app, how do I do it? Are there XMPP libraries that already implement all the required need protocols?