I believe that the user_defined_context.json file is unique to each job, as it contains the values the user entered in the form prior to submitting the job.
I believe the browser will cache values for form fields after the user successfully submits their first job, and when the user returns to the form, the browser will populate the fields. Perhaps that is the ‘caching’ you mean?
I don’t think the OnDemand server is caching from session to session or job to job. It does write out the data for each job in those directories so you can see what the options were when submitted.