NX is designed to work side by side with the existing X, not completely replace it, so the purpose of the NX versions of the X11 libraries is to override the system settings only when the applications are run under the control of the NX system. NX carries replacements of a very small subset of the X11 libraries (libX11, libXext, libXrender). These are the libraries used by agents. The other libraries are supposed to come from the default X setup. This makes it possible to run NX in many different X11 distributions, among them XFree86 and X.org.

See also the following article explaining why NX components don't use the -rpath linker directive to find the NX libraries:

https://www.nomachine.com/AR01C00133