During the long history of a huge organization, there must have been members who experimented with various possibilities, just like Spirit Medium Daly. They might not have understood the principle of the acting method in detail, but they acted out the name of the potion correctly anyway. They would have discovered the gist of it through the good feedback they received. As that accumulates through the generations of Nighthawks, unless the higher-ups were a bunch of curly-haired baboons, it would be impossible not to deduce the "acting method!"
Lord of Mysteries
Fantasy · Cuttlefish That Loves Diving
detail