[ksaun]

The entire system is too complicated, and the CGM too variable in accuracy, for such calibration to work in the way I think you are suggesting.

Each time the CGM is applied, the situation is different because of the exact position and various other factors. And the CGM is not 100% consistent.

You do/can calibrate the CGM as needed. For example, when the CGM first activates, standard practice is to check with a fingerprick to see how accurate the CGM is this time and (sometimes) calibrate. (As noted in other comments, the CGM and fingerprick are not detecting exactly the same thing.)

And the next time you apply the CGM (we use a Dexcom G6, which is changed every 10 days), any previous calibration is irrelevant. There's a lot of variability and many factors that can affect results (exact location, scar tissue from previous CGM application, recent exercise, a recent hot shower, etc.)

(I didn't explain that well, but hopefully you get the idea.)