Outside of "dinner" times, UA is serving a Cobb or Salmon Salad or a Tuscan wrap sandwich (turkey, cheese, and olives wrapped in a tortilla and warmed) in First. So this probably helps explain AS' offerings.
I am assuming during actual dinner hours they continue to serve a choice of two entrees with salad and dessert (I flew ORD-SEA dinnertime on Sunday, but didn't bother to upgrade since it was a two-class 767-300 and I was too far back to see the F meal service).