In Moodle 3.5.3. I created the situation for a user to submit a Data Request.
The Data Request was to Export the user's data.
The request was Approved by the SysAdmin or DPO and got the correct status.
Immediately after the next cron run the status went from Approved to Rejected.
The same process was validated on school.demo.moodle.net which I presume is Moodle 3.5.3? Also on this site the request goes from Approved to Rejected.
Same proces works fine on Moodle 3.5.2 where user is able to download after Approval.