I get that you can see # of seats days ahead (I posted my screenshot above for a flight next week)

I get that an International booking with multiple legs can get strung out 2+ days

The OP saw actual names on an upgrade list on SAT, 4+ days prior to his a single leg Companion Cert flight ATL-MCO. He didn't mention Int'l legs; how could he add them to Companion Cert flight anyway, and what would be the structure? He would have to be already checked in to his itinerary before SAT when he was able to see the ATL-MCO flight that was "more than 24 hours away as of TUESDAY".

OP, big favor, can you post your itinerary please? Or was it just ATL-MCO? Thank You!!