Well, seriously that art was concept art of Gridania from the original version of FFXIV (1.0) so I guess it was something the original development team thought of but never implemented (I always thought it was meant to be some kind of communication system with those... feathery things... being tags for packages and messages being zipped around on those lines) - either way, it's just one of those weird things that are tossed around during development and given form in concept artwork (which the loading screen was) only to never be actually implemented into the game itself. And there were plenty of things Tanaka and his original team had tossed around at various times for inclusion into the game but never appeared, so this is just yet another example of that sadly.

It would have been interesting to have in Gridania though!