Hello @joecox, and welcome to the community!
Unfortunately, that is a current limitation of our system, filtering linked records by their field values is currently not possible, but we do have it in our roadmap as you can see by this feature request: Deep filtering on both CMA and CDA
The current ways to get the behaviour you want, would be as you said, either adding a multiple links field on “Area” creating a “Double link” between area and development. Or, as you also said, request every development locally, and filtering them locally based on the Area that is linked, however that can scale quite poorly for a large number of development records.