It wasn't until today that Jiang Chen felt that the time had come, so he specifically asked Zheng Tian to tell Song Shi that he was already filming on set. Then, he asked Song Shi to visit him and take the opportunity to let Yuan Shu discover his identity.
Yuan Shu would definitely consider the big picture and wouldn't give up on this movie just because of Jiang Chen's identity. More importantly, this movie was far more important to Yuan Shu and Jiang Chen than the relationship between the two families.
After Yuan Shu recalled their interactions carefully, she knew that Jiang Chen was telling the truth, so she didn't dwell on this issue.
Now that Yuan Shu thought about it, many things that had happened before could be explained by this. This was also why Jiang Chen had given her a carefully custom-made gown.