Thank you very much, David. I didn't even consider the "impact" differential with plastic in the nozzle. I was also always calibrating cold. I never considered plastic at the tip might soften the hit and would change the readings. I was originally posting because I was curious about the deviations other users had, and I had no frame of reference for what "normal" would look like.
I will try calibrating at temps with no filament, and it should be more precise and will probably help with the z offset deviation. Why I thought calibrating a machine cold when it only functions hot is anyone's guess. Many thanks.