Hi Rani
My take on your questions ...
Why is it not to turn the interpolation to "OFF" ?
Because the target print may not match the printer native resolution. Vector is a basic interpolation method and will ensure adequate quality of the print.
Don’t we need to measure the RAW data without any intervention of any kind?
Whatever, the driver will "interfere" with the data for printing that's why you calibrate.
If the actual prints will be printed with "Fusion" there will be a difference in the outcome, no?
The interpolation method is not related to colour accuracy after calibration.
I can assure you, the job "{Q} printer target setup.job" works!
Terry