Most likely the result of the folks who trained him glossing over the laws and skipping right to ways around them. He probably learned things like, "If a driver won't roll down her windows and then has trouble pulling her ID out of her wallet, then you can make her get out of her car because she may be drunk." No, you can't, officer. He also probably learned that he could legally do certain things because of "officer safety." No, you can't, officer. Officer safety doesn't mean a damn thing legally.
I can almost guarantee he DID NOT learn that a police officer can't force someone to do anything unless he has probable cause to make an arrest.
If he had given her the summons to sign, then she refused to sign, he would have had an arrestable offense. However, as far as I can tell, he had no right to do what he did. Also, if he felt he had enough PC to make an arrest for obstruction or something(I see no way he could have), he could have done the same. In either case, he likely would have needed to inform her that she was under arrest before breaking into her car.