Haven't used it yet, but this would only do what you described if you're hitting the HDS for each call (which you may not) with some type of query. Per the guide, edits you make don't adjust the database itself, so likely wouldn't do what you want unless whatever you're doing a database lookup for subsequently looked for updates.
"Call variables edit operation updates the values of the variables within the particular call. All entities listening to dialog events receive the updated call variables through the Cisco Finesse notifications. If any CTI clients are connected to the same Agent PG, they also receive notifications of the changed call data though CTI call events. However, application scripts or databases that are used to populate the call variables are not directly affected by this edit. "
