If Toyota/Lexus implement function coding along the same lines as Mercedes (I imaging all manufacturers will use similar systems) then these regional specific codes will set using production line level coding systems. Once the cars emerge into the real world the service level systems such as Techstream will not have individual access to the lower level coding and region specifics will be grouped together to make replacing modules, due to failure or accident, simpler/quicker/cheaper.
One can change the region such as from UK to ROW (speaking from MB experience) to achieve a required change but one needs to be very careful that other 'grouped' settings aren't also changed, that may lead to unwanted changes in other settings. Maybe from miles to kilometres or gallons to litres, for example.