I'm a bit confused here with the circumference thing. If I take a wheel with a tire mounted and nominally inflated that is exactly 700mm in diameter and roll it out unloaded, I would get a circumference of 2199.115mm. If I load the tire such that it deflects 1mm, and do a roll out, I should get a measurement of 2192.83mmm or a wheel diameter of 698mm. The circumference of the tire did not change, but by loading the wheel, I made a shorter radius from hub to contact point. This is the distance that is measured during a roll out? I am displacing the sidewall and that allows for the hub to get closer to the ground. Yes the tire will 'squirm' to adjust to the new contact radius, but it won't be that noticeable. Consider the case of a fully flat tire. One should get the roll out number for the rim diameter plus the tire thickness.

Am I correct in this line of thinking?