I did not find if the user rights scans are purged automatically.
I have scans with multiple runs, and I'm unable to delete any of the runs.
The only way I found to clean up is to actually delete the scan.
You can see the tablespace usage of all scans.
In
main - discovery & classification - DB user rights select a scan then under
views, select
tablespace usage and it will show usage for all scans.
So you may be able to determine what needs to be cleaned up.