The best I was able to answer this question myself via searching the archives was bug# 53762 proposed by Branden Robinson, debian-x maintainer.
Should packages that contain binaries that run under the X-window system install those binaries into /usr/X11R6/bin? policy 3.2.1.0 states: _Packages using the X Window System should abide by the FHS standard whenever possible_; they should install binaries, libraries, manual pages, and other files in FHS-mandated locations wherever possible. This means that files must not be installed into `/usr/X11R6/bin/', `/usr/X11R6/lib/', or `/usr/X11R6/man/' unless this is necessary for the package to operate properly. The last phrase, 'unless this is necessary...' seems to be operative. Other than scouring the source for hard coded paths, is there a way to tell if a package 'needs' to be in /usr/X11R6/... ? FWIW the following is produced here: dpkg -S /usr/X11R6/bin/* |cut -f1 -d: |sort |uniq groff tetex-bin xbase-clients xcoral xfstt xloadimage xserver-common xserver-xfree86 xutils This is a current Sid/unstable system as of today. Thanks Gordon Sadler