It has to be for the same reason that creating a one-off prototype of a new plastic widget involves a much more manual process than a scaled-up assembly line.

It has to be for the same reason that creating a one-off prototype of a new plastic widget involves a much more manual process than a scaled-up assembly line. This is the first time this process will be performed on a real James Webb in space, and between each calibration step, they'll need to verify the results are as modeled in theory and adjust or reiterate if not.