Dealerships, just like any…
Dealerships, just like any other business have personnel changes. This can effect the proficiency level of the service department. One year they can have multiple techs that are really good with A/C, transmissions, and engine diagnostics. Then for some reason, the good A/C tech and engine diagnostics tech both move on. Now the dealership is advertising for more techs. They aren't telling customers they're currently lacking in those areas.
I remember looking at used cars at a local dealership. Their polishing and buffing guy at the time was not well trained and most of the vehicles on the lot looked horrible in the sun.