Did some more testing.
This is acting strange.
If you watch the status bar above the message bar; changing #4014 will update the Current Work Offset on the status bar, but it doesn't seem to change the core.
I set X offset for G54 to 1.00 G55 to 2.00 etc... and changed #4014 to 540, 550, 560, etc.. just to test all offsets, it won't update the position, it only changes what is displayed in the status bar.
So, I'm not really sure why you're able to change this and it update the status bar but not what Mach actually sees.