Discrepancy between XCB and X11 MappingNotify

[qqdpv04z at thepsauce.anonaddy.com]

> XKB-using applications appear to be expected to request that
> NewKeyboardMapping events be delivered to them, and that now includes
> all Xlib applications.
I'm confused. Let's say there is an X11 application out there which was made for
a libX11 version not using XKB (expecting to get MappingNotify events). Now when
this application is linked with another libX11 library built with XKB, then
this application will no longer work. I want to know whose decision it was to
forcefully include XKB like that, it just seems odd to me. But it looks like
this dates back to earlier than 2003 so it's only a deal in my hypothetical
scenario.

Thank you Keith, for helping me work through pretty much all "discrepancies" I
noticed.

There was one more thing in the Stackoverflow post which was what I mentioned
where XKeysymToKeycode(dpy, XK_F1) is used to "cache the modifier and keymap
information" which (I tried it, it actually worked) yields MappingNotify events.
This really does not make sense in my head.