Intake Gasket/Fuel Injectors

I recently took my 1997 Chevy S10; 4.3 liter; V6; 118,918 miles into a local repair garage because of a water leak in the lower intake manifold gasket. The truck was running smoothly at the time we drove it into the repair shop. After they replaced the intake gasket, we were told that there was a problem now with the fuel injectors being plugged. The garage owner stated that this happens often when they work on an older vehicle--sometimes during the mechanical work, "jarring" things around will dislodge dirt into one of the fuel injectors. The truck was missing on one cylinder and the check engine light was flashing as we drove the truck away from the repair shop. The repair shop owner handed us an estimate of $744 to replace all 6 injectors because as he put it "It would be impossible to know which specific injector was plugged."

Naturally, we had no faith in letting him do any further work so took the S10 to a Chevy dealer where they did a diagnostic check and found which specific injector needed replaced and that the oxygen sensor had been damaged which was causing the engine light to flash. The truck is now running very well.

My question is this: How likely is it that while working on an intake gasket, a fuel injector would become plugged/damaged and an oxygen sensor would get damaged simply because, "It's an older vehicle and you had some worn out parts".
It seems more than obvious to me (even though I am female) that this is WAY too much of a coincidence. In your professional experience, have you encountered instances of this situation?

Thank you so much for your help.