The self part of /proc/self/ns_id shows that this pseudo-file pertains to the currently running process itself.
The proc part hints that this is per-process, but Linux has not been consistent with this and lots of non-process-specific stuff landed in procfs (usually mounted under /proc), before adding sysfs (usually mounted under /sys) for new system wide information and settings. But /proc/self relates to the current process only.
So this file is new for every process and by default set to use VR-Mgmt and therefore needs to be changed every time the script is run.