So Boerd said
See, please don't take this as being flippant but unlike certain parties (not saying you) I like to run my country realistically. Do nice things for Prussia, Prussia does nice things for you. It's that simple. France has been extraordinarily nice to Prussia, so Prussia will respond in kind.
Here's my problem with this...it's not REALISTIC for France to be nice to Prussia. So it is a double standard. When other nations are nice to each other that seem kinda unrealistic (China/japan, France/UK) you get all up in arms because it's not historic. But because it's beneficial to you...you have no problem with it.