Accuracy of measurements
Can the Measure app measure to within plus or minus 1 mm, with or without LIDAR? Lengths to measure are from 0.5m to 4m.
The Related Article that brought you here says measurements are approximate. You would probably have to call Apple and ask for somebody in engineering to get your desired level of information.
Contact Apple for support and service --> "See a list of Apple phone numbers around the world."
Click here --> https://support.apple.com/HT201232