you set the "Enabled" flag as false, and you exit MM throught Alt+Q...
Do not disable Enabled for MRR. Just press Alt+Q.
only in this case, the rigs will be disabled.
OK, but if everything is dynamic (when you edit configs, or hashrates, power consumption...etc), don't see a reason why this part is different.
It's very useful for diagnosing problems on rigs. Example:
1) waiting for rent to stop
2) ALT + q
3) edit MRR config file to disable
4) rerun MM - to see the rig in action
By improving it you cut down 2 steps, it's much faster.