That is an interesting point, about the uninet being so ingrained in their culture despite being only a century old. However, it's possible that whatever came before the uninet was something similar to it, maybe like our internet. And even before that, I picture the early Ketrans as being a very imaginative, social, and interconnected race. All they get to do all day is flap their wings, and that would get very boring very fast if they didn't have lots of people to talk to and stories to tell.
As for how the uninet actually works, it almost seems to connect through the crystals themselves (hence why crystal-to-crystal transmission is so difficult). Perhaps the crystals have some sort of natural conductive properties? Like, they have some sort of internal structure (possibly enhanced by artificial construction to improve the pre-existing natural network) that allows thoughts to be quickly transferred from Ketran to Ketran, a little like artificial thought-speak? This would also explain why the uninet seems to be activated only when the Ketrans are docked with the crystal.
