We did not implement a way to hide the default WordPress filters, even if the columns are not there.
WordPress has it’s own hooks to hide the default filters, so you should be able to use these:

months_dropdown_results

Besides that, hiding a column through the screen settings menu (top right on overview page) does not hide the filter drop down for the column, which might be useful in some cases. But again, this does not work with the default WordPress filters.