I think Paul may have said something along the lines of it in a dev feed.
But I have observed this: In the turn notification list (right most tab, in the list panel on the right hand side of the main screen) you have an entry (when applicable) that states "There are x foreign ships in your territory without open borders permission". This notification is defined in the UIText.xml as the string for the ALERT_ForeignInZOC tag. Occasionally i see AI ships (of AI i don't have an open border agreement with) that are within my influence area but not near a star base or planet and those do not get selected when i cycle through the offending ships (by pressing repeatedly on the Goto button for the notification).
Assuming the ALERT_ForeignInZOC references the ZOC: The ZOC seems to be limited by both the area of influence and distance to planets/star bases. So either the ZOC is not equal to the ZOI (zone of Influence) or there is a bug in the Notification which indicates which ships are offending the ZOC.
One note is that all those ships that are not shown in the notification are outside sensor range of either planets or star bases, but are within sensor range of my ships. And i mean the sensor range of my ships at the beginning of the turn.
So it may be quite possible that the ZOC is the part of the ZOI that was covered by sensor range at the beginning of the turn. In which case it may be working as intended / designed.