Does Cornwallis not understand how a prisoner exchange is supposed to go
Out of all absurd scenes in the movie, the one where Ben tricks Corwallis into releasing his prisoners really goes over the top. Really, why would he do that? Why would Cornwallis release prisoners without demanding Ben release the "captured officers" he claims to have? It makes no sense. They call it a prisoner exchange, not a "release our prisoners and hope the enemy is being honest". No way Cornwallis would trust Ben to operate on the "honor system."
Really it would have been a lot better if the film had Ben and his militia go on a mission to capture some actual British prisoners they could exchange for their men. That would actually make sense, but nope they preferred to go the illogical route just for the sake of goofy comedy, which is clearly important to have in a movie that has civilians being tortured and killed on a constant basis.