I have. Clearly a problem and before the new COS rule. Outline version.

Return flight, two seats booked, job schedule went south and had to change to one day later, but had three days notice. Only one seat available one the day I needed among 4 flights. Booked single anyway.

Checked as continuous as possible for open seat and grabbed one when it became available. For curiosity checked original and it show two seats available.

Work schedule changed again. Had to move back a day. Found a flight with two seats and grabbed them. It made my flight a sell out. The one that I had instantly showed 2 seats.

Bottom line, amazing yield management.

(New COS rules lets me bump confirmed passengers, but I buy ahead so I do not have to inconvenience other people because of my problem.)