Synchronizing models in a VDB does not work quite as expected

Assuming I have a VDB which contains models,

1 - Modify one of the models
2 - Save the model
3 - The VDB editor shows the large "Synchronize All" button is enabled and the synch checkbox associated with the changed model is an empty checkbox. (The other checkboxes are large gray squares.)
4 - Click the checkbox (it now turns into the gray square - the large "All" button remains enabled)
5 - Save the VDB
Now the large "Synchronize All" button is disabled

If I click the "Synchronize All" button first, the checkbox is affected and the large button remains enabled until the VDB is saved. (If I click it again, it still goes through the synch process.)

I would expect the button and checkbox(es) to work together and that once all models are synched, the large button would be disabled even without the VDB being saved.