I’m not buyin’ it. Different types of plastic shrink different amounts, so .5% seems a little arbitrary. Also, it’s a well known fact that external dimensions of parts printed on lulzbots tend to be a little bigger than they are designed to be (especially in x and y), so if the idea is to make the part closer to the design dimension, you should lower the steps/unit, not raise it. Perhaps this is why all these people have dimensional inconsistency.
Just because that’s the way it’s always been doesn’t make it right, either.