To those of you interested, I updated the text with further discussion of the design-pattern - specifically about the fact that it reverses the dependency-relation between combined data, vs what one would have done by aggregating data within data.
This is also loosely related to OO in an interesting way - in that objects in OO have identities, and contain data and procedures - where here it’s individual data-sources (Socket.Endpoints) that have identities, which are carried across different data, and finally used to combine in a typesafe way.
I would be interested to hear if anyone also has experience with related patterns, and for what? Tyxml is one example.