Just as you can select whatever railroad gauge as a country (if you also build compatible trains, obviously) and have it work just fine no matter what you select--until you try to connect it to another country and then you need to have converters--, some physical theories have gauges like this that you can choose however you want and it will work fine (and be equivalent to a theory in any other gauge)--but if you want the theory to work with the next guy's theory you have to have converters.