Please review this thread, as I believe I have found an issue: https://community.powerbi.com/t5/Service/Slicer-values-with-row-level-security/m-p/541715/highlight/...
The same issue has been reported internally before: CRI 82130815. Please see below response from PG team:
By Design. RLS causes a Table-level filter based on the role, it does not update any slicer visuals. It is an "invisible" filter applied to every query that is generated.
Best Regards,Qiuyun Yu