Two data points from recent trips
Was flying DL ATL-JFK and continuing on Finnair to HEL on a separate ticket. Tried accessing the ATL club using my AY mobile bp fully expecting to be denied.
*scans bp*
"Remind me again of your status with Finnair?"
"Sapphire"
"Excellent sir, welcome in!"
Later on an arriving flight about an hour before the ATL club was about to close I presented my arriving bp on an AA flight from either ORD or LGA. Was let in without a problem.
So either ATL is staffed by clueless agents or maybe I'm just extremely lucky with accessing Admirals Clubs on arrival, maybe I should ask them for suggestions on lotto numbers next time I'm there.