Calibration without adjustment is a nonsense.
No, not at all - in fact adjusting precision instruments can be a nightmare.
If it's a reasonably modern piece of equipment where the adjustment is done electronically it might not be too be, however it's best avoided if the instrument is in spec.
If it's a mechanical adjustment then you can get all sorts of mechanical settling/whiplash type effects which can make it extremely difficult to improve the accuracy, even it it starts out of spec.
I
do tend to adjust stuff that I sell on ebay, if it's out of spec, but then I find myself running things for days afterwards to make sure they're not going to drift right back out of spec on me by the time the customer receives the item.
Even then, I can only reliably say that it was in spec when it left my hands as I'm sure a careless courier could bounce something which had trim pots or variable capacitors out of adjustment in all sorts of interesting ways once I have handed it over to their tender mercies.