Hello David
In the lesson, Rene has set up all routers and all interfaces within Area 0. The only time he changed that is when he tried the stub area option and put everything in Area 1 except for L0 of the Hub, essentially making the whole DMVPN topology a stub.
The alternative you suggest is a good one. Essentially you are saying that the backbone area 0 is assigned only to tunnel interfaces on all devices, and non-backbone areas are assigned to interfaces facing networks behind spokes and hub. This way, the hub and all the spokes act as ABRs, so any topology changes behind them will not affect the other areas. This also allows summarization at the spokes. The only issue you should remember is that each spoke router will need to maintain LSDBs for both Area 0 and its local area. As DMVPN topologies get larger, this may put a strain on typically smaller routers that may be used for such spokes.
Ultimately, OSPF is fine for small DMVPN topologies, however, it is to be avoided for larger networks. Even with the arrangement you suggest, the SPF algorithm will eventually become too resource-intensive (memory, CPU, and bandwidth) in a DMVPN topology. For this reason, EIGRP and BGP are the preferred routing protocol for DMVPN deployments.
I hope this has been helpful!
Laz