Make preferences changes take effect immediately from CLI
Send the System Preferences process a signal called the 'hang-up' or HUP, also known as signal number 1 as defined somewhere in a system signals.h header file. POSIX convention, I believe.

The quick and dirty:

sudo pkill -1 'System Preferences'


Replace System Preferences with Finder, or the PID of a relevant process.  Another quick and dirty:

for STALE in Finder Preferences locationd ; do sudo pkill -1 $( pgrep ${STALE} ) ; done


What a HUP signal should effectuate in the receiving process is an internal halt and re-evaluation, which usually includes a re-reading of any relevant config files. The process will not terminate, only 'refresh' itself.

Hope this helps.

F.