In my view the bit in red is tenuous at best. The opponent conceded the hole. As far as we know there was no prior discussion between the players of respective scores or net scores for the hole. This was a mistake in the opponent's internal thought process, not a miscommunication between the players.
Even if we do accept there was a 'mistake' around the application of handicap strokes and they do try to correct the 'mistake' in time, the opponent has incurred a one stroke penalty for lifting his ball (or ball marker). 3.2b(2) allows forgiveness if the the opponent lifts his/her ball based on a misunderstanding that the player’s statement or action was a concession but that is not the case here.
