I agree it does not seem to work, at least in Editor. Have you tried making a build?
Based on the API it seems it should perhaps say true, but the example given by Microsoft docs gives ParameterArrayAttribute as an example, and then they apply it by using the keyword in the args declaration, rather than as a pure decorator, sort of muddying the water as compared with yours. Perhaps it’s identical, I’m not enough of a C# weenie to know.