I
Dont know so far, but for now i interpret the situation differently here.
For me it looks like robin was there anyway (like we assumed last chapter, the girl with the patch over the face). So Robin and Sanji were able to get some information about different things and also about their kind of communication. And when they got the information they needed, Sanji kinda starts the changing of the situation by telling Robin to start. With his shoutout for help, Robin knew to start. Specially now, when BM gets beaten by robin, nobody will claim the Strawhats "hacked" their communication, cause they know Robin was there after Sanjis calling. Robin than thanks him for his patience, for waiting and getting beaten until they got their information.
At least that would be my interpretation of the situation.
For me it looks like robin was there anyway (like we assumed last chapter, the girl with the patch over the face). So Robin and Sanji were able to get some information about different things and also about their kind of communication. And when they got the information they needed, Sanji kinda starts the changing of the situation by telling Robin to start. With his shoutout for help, Robin knew to start. Specially now, when BM gets beaten by robin, nobody will claim the Strawhats "hacked" their communication, cause they know Robin was there after Sanjis calling. Robin than thanks him for his patience, for waiting and getting beaten until they got their information.
At least that would be my interpretation of the situation.