All form classes (including ModelForm) are subclasses of django.forms.Form?

In the Django docs, I've read the following statement:

All form classes are created as subclasses of django.forms.Form, including the ModelForm, which you encounter in Django’s admin.

I need you to explain to me please how ModelForm is a subclass of django.forms.Form!!!

The reason of my question is that I couldn't verify the docs statement through the Django project on Github. This is what I found there:

• in /django/forms/models.py the class ModelForm is subclass of BaseModelForm which is also a subclass of BaseForm (located in /django/forms/forms.py).
• in /django/forms/forms.py the class Form is a subclass of BaseForm.

So, as you can see, both django.forms.Form and django.forms.ModelForm are subclasses of BaseForm, but ModelForm is not a subclass of Form as the docs state.

Is it a mistake in the docs or am I missing something here?