Yeah the few times I have done the next gen check in with bag and paper tags I have done that peeled off one of the little bar code stickers and stuck it to the bag. Mainly because I have noticed the agents do that when they manually check in bags. I have never had anyone say not to do it and my bags have come through ok the times I did do it.

I had always assumed it was because if the bar code on the main bag tag was obscured in some way then the automatic readers could pick up the bar code on the little sticker.

I also believe if bags are packed in a container they peel off one of the stickers and put it on a sheet on the outside of the container. This is in case they need to unload a particular bag then they can find the container quickly. But I think there are three of the little stickers so it shouldn't be an issue.