I also can't think of any way that the ICM could make the crank sensor go bad, or the other way around. I've heard of both failing often, but never one taking the other one out with it. This is why I just avoid mechanics whenever possible...
The wiring for the crank sensor does originate from the ICM, or at least pass through it. Maybe that'* how they got confused.
Hopefully they at least got the part about the crank sensor being bad right!
It does make me wonder though... I had a bad ground from my ICM to it'* bracket, and it really acted like a bad crank sensor. The problem was that the ICM (without good ground) wasn't even supplying the crank sensor with it'* ground, so it couldn't function. Cleaning up that mounting surface fixed it. Probably not your issue, but worth a thought.