How do you know you weren't granted a special dispensation due to your Platinum status?Sure they can. I've had mine released from Cape Town.
In this case the seat is there, there is availability on a single leg, once the operator can see this, it becomes a technical issue. I've never had anyone say the phrase "married segment" to me. They've always just gone away and fixed it (granted, it usually involves being put on hold for a long time). I'm not entirely sure the average call centre worker knows what a married segment is.
There are plenty of reports that show the average person cannot easily unmarry segments.
In the call centre frustration thread, I remember someone (blackcat?) encountering this exact issue where a rescheduled international Qantas flight meant that their connection in Sydney was too short for their liking. Heaps of award availability on the connecting domestic flight, but the call centre staff refused to put them on a new flight. They said they were all blocked for new bookings or something of that sort. They tried multiple times with multiple call centres.
They were only successful after submitting a formal complaint in writing to Qantas through its complaints channel.