The "one number fits all" idea that DCS uses one single number for all sides might just fall short. Yes, the model is very simplified, but we only have one side of it, that is, the config file with the RCS values.
What people are not considering is that the underlining hardcoded calculation might have some clever, albeit simplified, algorithms that multiplies that basic RCS value, whatever it is, to a given ratio according the plane's angle. If one compares any given numbers of RCS signatures for fighter aircrafts, it becomes quite clear that there is pattern, something like 0 and 180 are usually about 1/2 that of 270 and 90 degrees.