Can't get Controlled Metamorphosis working in PoB

Just wondering if I'm doing something wrong?

I've put a massive ring CM Diamond into a hole at the end of one of my tree branches in PoB, but I can't allocate anything in that ring without PoB pathing to it (instead of allocating each node separately as I click it)

I've tried with From Nothing and that works exactly as I'd expect. Just cannot get CM working, so I can't test shit.