Refresher Question 13

[Jeff the Ref]

13. A–1 is erroneously awarded a one-and-one. A–1 makes the first free throw. A–1’s second free throw hits the rim and as B–1 is rebounding the ball, B–1 is fouled by A–2. The error is now recognized. Official cancels the free throw and cancels the common foul. Is the official correct? They say No! What aspect am I missing with this. I thought you could cancel hoop and related activity!