It's not desert solarpunk because solarpunk implies a hopefulness for the future that does not exist in Dune.
Dune and Dune Messiah are tragic cautionary tales which warn against religion and the great man myth. It is supposed to warn the reader that religions take a life of their own and become a tiger that you can grab by the tail, but can never let go of.
On top of that it's talking about oil as spice. If anything: it's diesel punk just with an abstraction around the diesel.