This phenomena seems more like, uhh, forgetting that lots of people haven't built the mental framework that makes things obvious to you. Not sure how else to describe it. Like, it'll just assume a lot of detailed knowledge as just something that everyone easily gets, and the very specific system they built on top of it is the only thing that needs to get documented.

For all that I love Datomic, their docs are a particularly egregious example of this, IMO. See: http://docs.datomic.com/query.html