Does this recipe want me to start with a dry-aged roast beef?
The recipe means to start out with it already dry-aged; presumably you'd just buy it like that because most people don't want to do that themselves at home. Dry-aging beef is a lot of work: you have to do it in large quantities, and it takes a long time.

The salting and leaving in the fridge is a separate thing. It's nowhere near dry-aging, and it works well for for meat in general, not just dry-aged beef. It's really just about properly salting it, with enough time for the salt to be absorbed into the meat, and for the moisture drawn out by the salt to either evaporate or be reabsorbed, leaving the surface of the meat nice and dry.