In case others stumble across this issue. Had this on RUTX_R_00.02.05.2, flattened the device and I can see the option now.
I was expecting a switch back interval on SIM2, we are at sea on VSAT at the moment so I'm unable to test any further but I intend to pull the primary and then put it back to see if the device will switch back once it's available again. SIM2 is a roaming card for when the vessel is outside the EU.