I'm not sure it is, I think RS deduces it from the mux list. So far as I can see, the region is only relevant to RS deciding whether to use your EPG data as a contribution to the overall RS EPG cache. The view of the EPG RS presents for any particular registered 'Fox is dictated by the relevant channel list.
I had muxes manually tuned, I got the tuner up first because there was something I wanted to record. Then I had time so I put in the USB stick to put custom firmware 3.13 on. Then it was time for the recording so I let it record that while I had dinner, and then after the recording I did fix-flash-packages which restored the packages. This being a transplanted hard disc from the dead box the disc portions were all still there. RS had to be registered though because it's a different box.
I didn't want to take the risk of strange behaviour. You believe that is all the region setting does, but you don't sound 100% certain. I decided better safe than sorry.
I wonder how many boxes have been moved over the years and are still reporting their old region to RS?
Not even that. It'll use the Network ID.
Not many because you need to retune to get it to work properly or even at all.
But unless you de-register the box from RS and then re-register it, RS will still see the box as being in its old region when it was first registered. I did a full auto tune and it did not fix my RS region even after the schedule sync'd.
Do you know for certain that the stated region in RS does nothing? Do we have access to the source code?