Coating a pre-finished floor?

Q: I recently installed engineered flooring with aluminum oxide finish. My wife wants to put polyurethane on it.

Is this a good idea?

A: I would not consider that a good idea, unless the finish on the floor is really beaten up and you have nothing to lose. It can be very tricky to impossible to coat these floors and gain adhesion. For the effort required to accomplish that feet, one might as well totally refinish the floors.