I don't think so. The X11 packages are prefixed to /usr/X11 entirely. Ther's no need to move stuff from /usr/X11R6/share to /usr/share.
I agree with Corinna: almost everything in an X11 package should be in the /usr/X11R6 heirarchy. The exceptions being: /etc/X11 stuff, and cygwin-packaging stuff like /etc/postinstall scripts & /etc/preremove scripts.
IMO, even cygwin specific documentation (which, in non-X packages, goes into /usr/share/doc/Cygwin/* and /usr/share/doc/<pkgname>/*) should go instead into /usr/X11R6/share/doc/Cygwin/* and /usr/X11R6/share/doc/<pkgname>/*)
-- Chuck
