This is nothing new. Paper Confirmed North American (HK49s) could always, upon request but subject to the agents willingness and savvy abililty, be collected prior to your travel day and noted in your record.
My CatmanDo Trois tickets for this coming March are done this way. I've never had a problem upon check-in. The record just shows a valid certificate authorization number already in the record (the same type of notation as if you used miles for the upgrade).
Now you have to ask yourself,
why would anyone want to do it this way and what are the advantages?
