Dataclass and Callable Initialization Problem via Classmethods

I found this weird behaviour where I don't know if I am the problem or if this is a python / dataclass / callable bug.

Here is a minimal working example

from dataclasses import dataclass
from typing import Callable
import numpy as np


def my_dummy_callable(my_array, my_bool):
    return 1.0


@dataclass()
class MyDataClassDummy:

    my_data: int = 1
    my_callable: Callable[[np.ndarray, bool], float] = my_dummy_callable

    def __init__(self):
        print("I initialized my Class!")

    @classmethod
    def my_factory_with_callable_setting(cls):
        my_dummy = MyDataClassDummy()
        my_dummy.my_callable = my_dummy_callable
        return my_dummy

    @classmethod
    def my_factory_without_callable_setting(cls):
        my_dummy = MyDataClassDummy()
        return my_dummy

    def do_something(self):
        print("This is my data", self.my_data)
        print("This is the name of my callable", str(self.my_callable))
        return self.my_callable(np.empty(shape=(42, 42)), True) + self.my_data


@dataclass()
class MySecondDataClassDummy:
    my_data: int = 4
    my_callable: Callable[[np.ndarray, bool], float] = my_dummy_callable

    @classmethod
    def my_factory(cls):
        my_dummy = MySecondDataClassDummy()
        return my_dummy

    def do_something(self):
        print("This is my data", self.my_data)
        print("This is the name of my callable", str(self.my_callable))
        return self.my_callable(np.empty(shape=(42, 42)), True) - self.my_data


if __name__ == '__main__':
    # this works
    my_first_dummy = MyDataClassDummy.my_factory_with_callable_setting()
    my_first_dummy.do_something()

    # this also works
    my_second_dummy = MySecondDataClassDummy.my_factory()
    my_second_dummy.do_something()

    # this does not work
    my_other_dummy = MyDataClassDummy.my_factory_without_callable_setting()
    my_other_dummy.do_something()

case1: initialize with factory, initialize with my own init and then set the callable explicitly after initialization (allthough there is a default value) - works

case2: initialize with factory but don't explicitly code the init() myself - works

case3: initialize with factory, initialize with my own init and not set the callable explicitly after initialization (because this is why I have default values, isn't it?!) - doesn't work but throws the error:

Traceback (most recent call last):
  File "my_path/dataclass_dummy.py", line 63, in <module>
    my_other_dummy.do_something()
  File "my_path/dataclass_dummy.py", line 33, in do_something
    return self.my_callable(np.empty(shape=(42, 42)), True) + self.my_data
TypeError: my_dummy_callable() takes 2 positional arguments but 3 were given

So now I am wondering, what I am doing wrong in the third case.

I am using Python 3.8 and numpy 1.20.2