Booking through the Ultimate Rewards Portal is no different than booking through Expedia or Orbitz, just another OTA. Chase gives you the PNR upon booking. You can enter that on Delta's site and add you r Skymiles number of it doesn't take. Though I've never had that problem. In fact, it's so instantaneous that within seconds of booking I can open the app and see my new trip right there; though I may not have a ticket number yet.