There are 2 types of calibration, offset and crosstalk.
If you don't calibrate the offset, the sensor could be up to 2cm off. But that particular chip will be that far off forever.
If you have a cover glass and do not calibrate, near objects would still be about right, but as the target got farther away, the sensor would under-range. And it's possible to get a 'false target' when there is no target due to the number of photons reflected by the glass.
Best bet is to build a number of units and crosstalk calibrate them. Then use these calibration numbers for all you devices. However this approach counts on having a constant distance between the sensor an the glass and a constent quality of glass.
Another approach is detailed in the video,
VL53L1X Dirty Cover Glass: https://youtu.be/BHM2CZVXZGc
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