No, really, it isn't. Pros - even experienced cyclists without the talent to be pros - can experiment with cadence in this way because they know what they're doing and they have the power to back up their experience. And I'm not saying that training with cadence doesn't have its uses, in fact in another thread I said I thought it was a good idea for varying, and increasing the intensity of, one's workouts. I'm just agreeing with RChung's basic point (which I don't think many in this thread have taken on board) which is that asking a new cyclist to aim for some abstract number, as opposed to experimenting to find what feels comfortable and working on that in the appropriate context, isn't good advice.