That actually does not match my understanding; if I remember correctly, the GTK people felt that emacs was doing something that they did not want to support, and since no "well behaved" GTK applications had reported the problem, they were thus were unwilling to continue. I might be misremembering. 

Emacs added that code as a response to the GTK bug, because calling abort() itself is minorly cleaner than allowing the crash from _exit() in the library. 

At heart, emacs is trying to use a niche feature that was spec'd but never fully implemented in gtk/gdk. Nobody else wants to use that feature, because there just aren't that many apps that want to hop around between open and closed displays (like emacs --daemon does) AND that also have a lot of long-lived state (most would be fine with simply closing and restarting). Web browsers are the nearest candidate that comes to mind, and they have already invested large-to-massive effort in the alternative "run distinct copies everywhere, including your phone, and layer on a sync service for the few places where you might care".

This creates an environment where the GTK maintainers weigh a bunch of groddy low-level work to support a feature almost no one wants on one side against a client base that has the highly-functional "just use Lucid" alternative on the other. This world doesn't produce a lot of motivation to solve the problem, and the solution will likely (if I understand the decade-plus-old bug-thread) require fairly low-level changes to gtk/gdk, so the solver needs to be very familiar with gdk internals, so the friction is quite high. In the meantime, X11 is due to be obsoleted every few years for the last decade...

~Chad