Clock spring replacement recommendation by dealer mechanic

The dealer is right. The clock spring is not touched when replacing the airbag. If they had done something wrong, the clock spring would not have lasted three months. The only thing they can do to damage the clock spring requires the steering shaft to be disconnected from the rack and pinion steering gear, then the steering wheel must be turned at least one full revolution one way or the other, then the shaft must be reconnected. That is a mistake to be aware of when replacing the steering gear, not the airbag.

The clock spring is a wound-up ribbon cable in a plastic housing, under the steering wheel. It is just long enough to wind up fully and unwind fully when the steering system is turned full-left to full-right, and no more. With the steering shaft spun one revolution, then reconnected, turning the steering wheel all the way one way will either wind the ribbon cable too tight and tear it off, or it will unwind too far and fold over on itself. Tightening too much will snap the cable the first time you turn the steering wheel to its limit. Unwinding too much takes longer to damage the cable. It has to fold over multiple times before it cracks apart. That can take as much as a week or two.

Broken clock springs are a common failure on every car brand. Fortunately the diagnosis is fairly easy when there are so many systems involved, and they all act up at the same time.

Besides not being involved in the recall service, the clue is the "three months". Once a mechanic touches anything on the car, they get blamed for everything that happens to it after that, even years later.