I've found most of the larger tire sizes to be pretty close on the stated size. I think the shady reporting is usually on the smaller tire sizes so manufacturers can claim a "lighter than the competitor" advantage, when in reality they're saying it's a 25 but it's a 24.
I have heard of some going the other way, though. Grand Bois Cypress tires run 1-2mm larger than stated; a buddy of mine couldn't clear a pair in his fenders due to misrepresented sizing.