Follow up: this didn't sound right, so I called again. First, they claimed that I didn't have a Delta number in the system (I did). Then, they said that the number did not reflect my Delta status (I've sent them screen shots to prove it did). Then they conceded and allowed me to choose a premium seat free of charge (but not for my travel companion on the same itinerary). They also confirmed that lounge access was not offered to "members of other airline FF programs". I may want to challenge this on the day of the flight, we'll see. First world troubles for sure.

Shuly