"So, X11 network transparency is more or less a myth. It's not transparent, and in most cases, it's not even networked."
I've programmed in Xlib, as well as in Xt (ugh). It's true that programmers writing X apps have to program to X, which makes the network's presence pretty evident, but once you've done that, you get network support whenever a user wants to use it.
The fact that "in most cases it's not even networked" is true, but irrelevant. In most cases when I'm programming I don't touch the mouse, but that doesn't mean it'd be acceptable to get rid of it.