Hello Rafael
Rene mentions in the conclusion that summarization cannot be applied. This is not a limitation of DMVPN Phase 3 but a limitation of OSPF. Summarization within the same area cannot be implemented. For this reason, all spoke routers will have to have specific routes to all other destinations, something that is not ideally efficient.
On a side note, the purpose of DMVPN Phase 3 is to allow spoke routers to directly communicate with each other rather than to communicate via the hub. This is done using NHRP redirect on the hub which will instruct the hub to inform spokes that they can communicate directly. Secondly, it is accomplished using the NHRP shortcut feature in the spoke routers which allows them to make changes to the CEF entry when they receive an NHRP redirect message from the hub. More on this can be found here:
I hope this has been helpful!
Laz