Even without vectors, if the user has 3 call-appr and the last is restricted to use only for conf/transfer per page 2 of the station form, the 3rd will hit coverage.
Does the user need more appearances and might, for example, make one or more outbound calls, still want to receive up to 2 calls and upon receiving a 3rd go to voicemail?
If so, make a X port station with 2 call-appr, don't restrict the last appr, and put 2 brdg-appr of that extension on the user's phone