"the Captain got told off by flight ops". Sorry to burst your bubble folks but the Captain was not in the wrong, he was perfectly correct in trying to keep the operation running with a legal number of cabin crew and Flight Ops do not tell captains off for such trivia as this. If they even noticed it would simply have been to say "Oh well, you tried your best."
I agree on this. I don't believe for a second that Flight OPS told off the captain for trying to leave one down. Flight OPS is trying to run the operation and they would probably have been pleased if the flight had left one down to save them a crew member!