Agreed. There is no harm that can be done. I was just pointed out that the service manual has a DTC code listed for it. Perhaps it only looks at it when the solenoid is connected, but it clearly is looking at voltage and capacitance in the circuit from the system diagram.
Basically, there is no harm it can do, The only harm would be it either triggers a code that is detected during an emissions check or a Tech looks for it similar to how they physically look to see if you have cats....
go ahead and unplug it.
Another user that just installed the FRPP pack with the K&N filter, the tune and the mufflers just confirmed that unplugging the solenoid caused a DTC code to be read when he went to install the tune. He had to plug it back up to clear the code.
In short, unplugging it will not do any damage, but it will eventually trigger a DTC code as indicated in the shop manual.
2011 Mustang GT Premium, Brembo Package, 3.73, Manual, Black, C&L Racer Intake w/ Bama Perf tune