As the Chatham Cup is a NZ Football competition they have the final say as to when and were cup games are played including KO times so NZ Football must have OKed it. I know that due to the time Olympic are flying out, and allowing for extra times and pens that the Chatham Cup cannot kick-off any later the 2pm and if the Women's KO Cup game is kicking off at 12.30pm then sadly the two games cannot be played at the same venue.
There's rules AW, and then there's common sense. As any ref will tell you, common sense prevailing is usually the best course.
Common sense is one thing but tell if one game has to kick-off at 12:30pm and the other at 2pm how can they be played at the same venue, would get away with it for a league game but not a cup game with the possiblities of extra time and pens.