Re-grinding a cam, educate me please

Picture a V8 cam shaft. It has 16 (changed from the erroneous 18) separate 'cams'; 8 for intake and 8 for exhaust. One side of each cam is a smooth round circle ( this is the bottom of the base circle), and the opposite side (lobe) has the big bump that pushes up on the lifter. Lets say that your cam had an intake lift of 0.445" when new. That means that the tip of the lobe is 0.445" above the base circle. Lets also say that after 100,000 miles the lift is down to 0.440" due to wear. So the cam now has 0.005" less lift than before. A cam re-grinder does not need to add material to the lobe. Picture having a machine that can accurately grind 0.005" off of the base circle side (leaving it as a smooth accurate circle) and leave the lobe side alone. You now are back to having the tip of the lobe 0.445" above the base circle. That is a gross oversimplification, but the overall idea is correct. They will actually need to grind a little more than 0.005 off the base circle side because they do need to work on the lobe side a bit to restore the correct duration. Once the cam has been reground, the tip of the lobe will be 0.445" above the base circle, so you will have 0.445" lift. However, since they had to grind down the base circle side, that means that a micrometer measurement of the cam from the tip of the lobe to the bottom of the base circle side will be less than it was before. So you may very well need new pushrods.