IIRC, this isn't what we were told by executives in the Q&A session at the DL ATL DO. I remember comments to the effect that PDB is a DL service standard, although it can be eliminated for cause (my words), such as late arrival of the incoming aircraft, late catering, illegal at that location, etc. There was also some discussion of not every drink being available on international because of the duty free status of normal drink carts.