Querying issue with ForeignKeys where db_constraint=False

[Alex Bailey]

models.py

from django.db import models

class Person(models.Model):
    name = models.CharField(max_length=25)

class Book(models.Model):
    foo = models.ForeignKey(Person, db_constraint=False, on_delete=models.DO_NOTHING, related_name='foo')
    bar = models.ForeignKey(Person, db_constraint=False, on_delete=models.DO_NOTHING, related_name='bar')

setup

from .models import Book, Person

alex = Person.objects.create(name='Alex')

Book.objects.create(foo=alex, bar=alex)
Book.objects.create(foo=alex, bar_id=999)
Book.objects.create(foo_id=999, bar=alex)

shell

>>> from django.db.models import Q

#Correct: Returns both books where foo__name == 'Alex'
>>> Book.objects.filter(foo__name='Alex') 
<QuerySet [<Book: Book object (1)>, <Book: Book object (2)>]>

#Correct: Returns both books where bar__name == 'Alex'
>>> Book.objects.filter(bar__name='Alex')
<QuerySet [<Book: Book object (1)>, <Book: Book object (3)>]>

#Only returns one book where both foo__name and bar__name == 'Alex'
>>> Book.objects.filter(Q(foo__name='Alex') | Q(bar__name='Alex'))
<QuerySet [<Book: Book object (1)>]>

I am working with an existing DB where it is possible for a Person to no longer exist, hence the lack of db_constraint in the ForeignKey.

Books can refer to non-existent Persons but it still seems like expected behavior would be for the queryset OR to return all 3 books. I believe this is coming from the Django ORM doing an INNER JOIN.