I couldnt understand why they totally dismentalled the pump while noting to replace. I think the batter way to wash the pump externally first before dismentalling and check for diesel quentities per cylinder.
Sometimes the pump when sitting for a long time gets dirty from the dried diesel, like a laquer so a good clean and refit is a good solution for it to fully work again, also the pump elements might get dirty too with dirt and oil. It will definitely need calibration to work perfectly again.
Rotating that pump in the vice is annoying and it's like that mechanic has a very small line if vision He can loosen a bolt he can't see It had to be right in front of him to loosen the bolt
Congratulations, let me give you some constructive criticism, when testing an injection pump, first install the caps under the pump and then, lubricate it. Once I was testing a Volvo X 10 pump, low on lubricate oil. The pump almost melted on the test bench.