[axman]

 sanst, on 2020-September-01, 14:39, said:

Where does general bridge knowledge end?

General Bridge Knowledge is comprised of that which is derivable by theory or general experience that does not depend upon partnership agreement. GBK includes the content of the law and the conditions of the deal; also it is GBK that a player’s and dummy's hands, the vulnerability, who is dealer, the legal auction, the rules of the game, and the opponent's system may, or not, influence the judgment taken in treating the partnership’s method in bidding and playing a hand.

[nige1]

 sanst, on 2020-September-01, 14:39, said:

Where does general bridge knowledge end? If you start announcing such calls, you will probably confuse less experienced opponents and make you look like a pedantic fool in the eyes of experienced players.

Sabst makes an excellent point. Many Bridge players solicitously avoid confusing opponents with the truth. Understandably, they're averse to being labelled Pedantic Fools. They rationalise their idiosyncratic agreements to be General Bridge Knowledge. -- even when only a telepath could be aware of them -- unless disclosed. (e.g. the convention described in the OP). Give equal credit to directors, who rule in their favour.