We saw this too in the lab. You have to reboot them after they have all joined the cluster then they will show up in portal mode. A word of caution. With IAP you can not designate a portal or point AP manually. They will automatically elect which mode to be in depending on their connection. You also have to have VLAN 1 as the native on the wired port of the point AP if you want to use it as a trunk.
If the switch on the portal side has BPDU guard enabled it will shut down the port when the point AP connects and starts sending packets which will cause that AP to change to a point instead. Eventually every portal could become a point and then you have a giant mess...
We have had this happen and Aruba was as surprised as we were. Just make sure your BPDU guard is off.