That wouldn't/couldn't happen. Your stove is already (or should be) grounded, so you can't get the frame of the stove to be energized. In the other way, the only way that the faucet could become energized is what I mentioned before: some damaged wiring somehow makes contact with the metal piping. It is a long shot as the damage would have to be right where the wire crossed the pipe and the pipe would have to be touching the wire. Bonding the plumbing would prevent this, but I really wouldn't worry about it.
In my case, I bonded, but for several reasons:
1. metal pipe coming into the house and using it as a ground rod
2. easy access during basement reno
3. did the work myself, so the only cost was a bit of wire
In your case, it looks like he is trying to make some money off of you.