Kuki et al,
The sticker seems to be "hit and miss" but the agents at the terminal also have a list of passengers whose information is complete. If all of your information -- including a credit card for your shipboard account -- is in the system, you'll be able to do the advance check-in.
If you have express check-in, the only coupon in the ticket package that you need at the check-in desk is the signature card for your shipboard account. You tear that out, sign it, and exchange it for your cruise card. That's it.
Some facilities do have a separate express check-in line. It all depends upon the local port.