[pohl]

Sorry for the pedantry, but doesn't expecting the terms to relate to things in a different context go against the very nature of jargon?

Jargon is "technical terminology unique to a particular subject." [wiktionary.org]

I imagine that when one is discussing OTs and how they relate to the federation protocol, these terms would be very useful. Sure, you could talk about nodes and edges in a graph, but there are many graphs of many types in any large system. These terms refer to specific kinds of nodes in a very specific kind of graph.