The "map" that is installed or downloaded is a strategy that cannot be forgotten on this ICU,ECU,computer or whatever you want to call it. This is my educated opinion. There are other mechanics that will agree you will not harm this unit by disconnecting the 12v power supply from it.
You can cause harm from a voltage spike by disconnecting and reconnecting(1 in 1,000,000 chance) the battery or ESD (electro static discharge) from static electricity by touching the internals components of the processor.
p.s. I am not going to argue with ANYONE about what is done on any website.