Those numbers are as close as brand x compared to brand y compared to brand z in the same size, or even different tire models of the same brand.

Loaded radius within under an inch is pretty much the same size. 

Overall diameter will vary with different aspect ratios because of the difference in squat with the smaller wheel/more rubber. 

For instance the row crop tires I run on my sprayer and the floater tires I used to run on the rear of it for burndown run together okay with the axles tied together and locked in, but looking at them the rear ones looked a good 6" taller.  My skinnies are 95 aspect ratio and the floats are either 55 or 50's.  44" wheels vs 25" wheels.  If the skinnies were squatting as much as the floats, the rims would be hitting the ground!