As such it is the only directory which will need to go in each user's path.
Note that all "official" XAS commands are binary executables, there are no such thing as officially supported XAS (shell) scripts because of the original architectural choice of XAS to be system-independent (at the time it was designed that meant running on VAX VMS and several Unix flavours), i.e. not dependent of any shell.
As such this directory will contain system-dependent files. A multi-architecture support of XAS will require separate bin directories under different $XASTOPs
Note that because of the above architectural choice, some XAS commands are implemented as front end wrappers which chain to another executable (i.e. they run for a while then are overlaid by another executable). This will be specified in the program specific manual page.