I was in case #2 for a while, and tbh it should be treated as the building's fault for being this way, cause ambiguous ZIP codes aren't really supported. The IRS refused to send my refund, mail kept getting lost, and various things involving credit kept flagging me for fraud. Also it looked like a PO box to some systems but wasn't. My solution was to move, or I could've gotten an actual PO box or other mailing address.

But polygons support it fine, they just overlap.