pytest_snapshot snaphot removal

Question

If I have a tests folder structure like this -tests --init.py --test_main.py

And my test looks like this:

from pytest_snapshot.plugin import Snapshot

def test_my_func(snapshot: Snapshot) -> None:
    output = "test output"
    snapshot.assert_match(output, "testing.txt")

When I run pytest tests the initial run fails.

Then I run pytest tests --snapshot-update and it creates the snapshot.

Now the pytest tests run passes.

When I remove the test_my_func() function and I run pytest tests --snapshot-update --allow-snapshot-deletion the snapshot does NOT get deleted.

The steps above are a minimal reproducable example of what I wanted to test. The --allow-snapshot-deletion flag does not work as expected. According to the pytest_snapshot documentation, it should remove the unused snapshots... https://pypi.org/project/pytest-snapshot/

Am I doing something wrong or is the --allow-snapshot-deletion flag not working correctly?