Historical model does not allow deletion in reverting django data migration

I'v two models

class A(models.Model):
    index = models.SmallIntegerField(primary_key=True)
    audio = models.FileField(null=True, blank=True)
    x = models.SmallIntegerField()
    y = models.SmallIntegerField(null=True, blank=True)

and

class B(models.Model):
    b = models.ForeignKey(B, on_delete=models.CASCADE)
    index = models.SmallIntegerField()
    audio = models.FileField(null=True, blank=True)
    image = models.FileField(null=True, blank=True)

I made a data migration that initializes model A objects (every object also creates B objects with it and every created B also creates C objects with it.) Here is the migration:

from django.db import migrations


def create_as(apps, schema_editor):
    A = apps.get_model('super_app', 'A')
    B = apps.get_model('super_app', 'B')
    C = apps.get_model('super_app', 'C')  # C has FK referencing B
    # Some logic here that creates instances of A (also creates B and C)

def delete_as(apps, schema_editor):
    A = apps.get_model('super_app', 'A')
    A.objects.all().delete()


class Migration(migrations.Migration):

    dependencies = [
        ('super_app', '00xx_the_very_previous_migration'),
    ]

    operations = [
        migrations.RunPython(create_as, delete_as)
    ]

The migrations is applied forward successfully.. but when I try to revert back the migration (Which should call delete_as) I'm always having this error:

ValueError: Cannot query "B object (757)": Must be "B" instance.

I've been trying and digging but no clue why this happens! Note: The type of models in migrations are historical models (__fake__.{MODEL}) I tried to use the latest state of the model by doing:

def delete_as(apps, schema_editor):
    A = apps.get_model('super_app', 'A')
    from django.apps import apps  # FIXME. This gives latest models state.
    B = apps.get_model('super_app', 'B')
    B.objects.all().delete()
    A.objects.all().delete()

And it worked without problems and I could revert the migration!! But, according to Django documentation, this should not be used.

Any ideas about why this happens?