No, not consistent, and they aren't alone. I've tried multiple pairs of Shimano/Northwave and Specialized, they all fit slightly different from model to model.
It's why I won't be buying cycling shoes online anymore, these companies are far too unreliable. In comparison, I know when I order a size 8 running shoes from Asics, it will fit. I can't tell you why Shimano 40 will fit the same in one model as a 42 in another model.