Found by Dirk Lemmermann,

So elegant now, to describe these bugs with a simple unit test. :)

@Test
    public void shouldCollectBoundListProperty() {
        JMemoryBuddy.memoryTest(checker -> {

            // given
            ListProperty<Object> listA = new SimpleListProperty<>(FXCollections.observableArrayList());
            ListProperty<Object> listB = new SimpleListProperty<>(FXCollections.observableArrayList());

            listB.bind(listA);

            // when
            listB.unbind();

            // then
            checker.setAsReferenced(listB);
            checker.assertCollectable(listA);
        });
    }