Easy there. You're generalizing based on one person's claim, not even something that can be verified. He works on mountain bikes in a shop?
Never have I witnessed such chicanery at any of the shops I have worked at. As Velocipedio pointed out, there is no incentive at all to do such things, based on the generous employee discounts offered by most vendors. Never mind that the employee would have to sneak something like that out under the boss' nose while hoping said bike never returned to the shop, to avoid the altered parts would coming into question.
The more you and your hubby spout such unsubstantiated nonsense (see one of his posts), the more this seems like trollsville.