most slide films are balanced for around 5500 I think. for the most part so is B&W films as they seem to take an extra stop to expose them when under tungsten lights. It's not so much which is right or wrong, it's a matter of testing to see what works with your setup. It's my opinion this is why so many people fiddle with their asa's. When you combine this fudge factor with trying to understand the zone system it's no wonder people get all confused.

The test data that is out there shows that how a meter is color balanced also determines it's sensitivity to illumination. Think of it as a band pass filter.

I do agree that if you take 10 meters and compare them side by side you will probably get 10 different readings. However the error should only be within 1/2 stop either way. Moreover, if you did a plot of Euro meters compared to Japanese meters you will see the graph will show a 1 stop spread on average between the two, deviations normalized.