That's correct. In that scenario, it would behave just like the original OEM single sided safety body.

Another option to milling the existing ambi safety body would be to replace your original ambi safety with an early safety body that used a screw to secure the lever (or a single sided one if it could be found) This would maintain the integrity of your current ambi safety body. The right side lever on the replacement, if there was one, could be removed and the screw returned to the assy without the lever in place.
An 8x32 pan head hex drive screw could also be used if the original phillips head screw was unavailable.

__________________
Ret. LE, FA Instr, S&W Armorer