Whoever uses violence on the spot or threatens to hide stolen goods to resist arrest or destroy criminal evidence because he commits theft, fraud and robbery as stipulated in Article 269 of the Criminal Law shall be punished (robbery) in accordance with the provisions of Article 263 of this Law.
Wang, Dai and Gao used violence to rescue Zhang. With the help of Dai and Wang, Zhang resisted arrest and escaped Feng's pursuit. If Gao knew that Zhang was arrested and rescued afterwards, he should also be a criminal of robbery.
As for whether it was "on the spot", I think that although there was a certain time interval after Zhang was arrested, the other three people went to rescue him, but it can still be understood as using violence to resist arrest on the spot.
Or Wang, Zhang and Dai are accomplices. Personally, I don't think this is a transformed robbery. Robbery is an act of occupying other people's property by violent means for the purpose of illegal possession. In this case, the people involved did not take the steel away at last, just to save their accomplices. As for Gao, I think that if you know the truth, assisting Wang Dai's Gao also constitutes a crime, but it is not theft or robbery. Because his subjective aspect does not involve the constitutive elements of these two crimes.