That sounds to me as very illogical. You are afraid that, for the case of a function taking optional arguments, a beginner who uses & in front of the function name, might forget to use parenthesis? (Note that if the function requires arguments, omitting the parenthesis in combination of using & is a syntax error, and if the function doesn't use arguments, passing in some extras isn't going to hurt)

Sounds too rare of a problem to get all dogmatic about.