The current implementation of tkinter.OptionMenu creates the widget in a manner different from all other tkinter widgets.

def __init__(self, master, variable, value, *values, **kwargs):

Here is a proposed method to deal with this widget.

    def __init__(self, master=None, cnf={}, **kw):
        """Construct an optionmenu widget with the parent MASTER,
        Supports kwarg configurations from MenuButton.
        """
        values = kw.pop('values', [])
        value = kw.pop('value', None)
        kw['borderwidth'] = kw.get('borderwidth', 2)
        variable = kw['textvariable'] = kw.pop('variable', StringVar())
        variable.set(value)
        kw['indicatoron'] = kw.get('indicatoron', 1)
        kw['relief'] = kw.get('relief', RAISED)
        kw['anchor'] = kw.get('anchor', "c")
        kw['highlightthickness'] = kw.get('highlightthickness', 2)
        callback = kw.pop('command', None)
        Widget.__init__(self, master, "menubutton", cnf, kw)
        self.widgetName = 'tk_optionMenu'
        menu = self.__menu = Menu(self, name="menu", tearoff=0)
        self.menuname = menu._w
        menu.add_command(label=value,
                 command=_setit(variable, value, callback))
        for v in values:
            menu.add_command(label=v,
                     command=_setit(variable, v, callback))
        self["menu"] = menu

I have replace the kw dict with dict.pop and dict.get methods to allow users to override the standard values while keeping the style the same.
I have also conformed the init args to be the same as standard widgets using master, cnf and kw with default values.

This should be a drop in replacement to the OptionMenu.init method.
(FYI i dont know how to do PRs yet and the doc string probably needs editing.)

Linked PRs

gh-101284: Allow passing Menubutton options to tkinter.OptionMenu #151959