Why does my Django models.Manager return all objects on a relationship?

I don't particularly understand what's going on here, but it seems that super().get_queryset() doesn't do what I think it does?

I have 1:N relationship, and the default FK reverse lookup works:

>>> for thing in this.thing_set.all():
...   print(thing.this)

Each one of these is This.

However, with my customized:

>>> for thing in this.thing_set.by_date():
...   print(thing.this)

Will produced This and `That*

class ThingByDateManager(models.Manager):
    def by_date(self):
        return super().get_queryset().order_by("start_time")

That's all there is.

class This(models.Model):
    name = models.CharField(max_length=255, primary_key=True)

class Thing(models.Model):
    start_time = models.DateTimeFiled()
    name = models.CharField(max_length=255)
    this = models.ForeignKey(This, on_delete=models.CASCADE)

    objects = ThingByDateManager()

(might not have those models perfectly written, but I'm hoping it's just something silly with the queryset or something)

Why doesn't this correctly filter my objects by this, instead returning all of the Things?

return super().all().order_by("start_time")