Yes, most likely. However, it seems to me that user settings data on Facebook is distributed (the data is stored in multiple places, rather than all the data for all users stored in one place). If that is the case, then it is possible that sometimes the necessary data is not available with regard to a specific (other) user at a specific time. The proper assumption (on the part off the software) in that case is the most conservative (locked-down) setting.
You can see this in action, quite often, if you play FarmVille. Sometimes some of your neighbors either vanish or become listed as "Unreg." (and then later come back, as if nothing had happened).