Were you previously able to assign the "optional" customer, and it is just now no longer working?

I ask, because I just discovered this feature and in the online interface, it works for me. But if I go back and open the bill, there is no way to see or edit the customer it was assigned to. I would like to assign customers to bills, but I am worried this is a feature that is included as a "teaser" for upgrading to the next level and that it just doesn't work right without the upgrade.