Carol, you stole my response!! But I will drop it here anyway:

It's been my experience that seat changes are most likely the result of an equipment change.

FWIW, it's highly unlikely that an airline would cram-in additional seats. The reason for this is that all airlines are required to run tests (with test live subjects) to ensure that the plane can be evacuated (in an emergency) in 90 seconds or less.

This is why seatbacks are required to be in the fully upright and locked position for take-off and landing. Absent this requirement, an airline would have to test an nearly infinite number of seat-up-seat-down configurations to ensure that every single combination meets the FAA 90-second emergency evacuation requirement.

And, yeah. That seafood boil photo made my mouth water. Hope it tasted as good as it looks!!!