To govern is to control. If it's voluntary is not government. Precision in language is important. Also I havnt met a minarchist that wanted their night watchmen government to be voluntarily funded. If such a person exists then I agree with you that they aren't minarchists. But that doesn't mean that minarchists don't exist. And for the ones that do exist -- the distinction between them and libertarian principle is an important one to continue calling out.