Wayne it does appear to be a Premium specific defect. Looks like since v2017 there is an additional WRITE to the SQL worktable in the Populate Work Table routine. That is fine on non-sql but on SQL the worktable (in TempDB) is always created with no primary key. This means every time you WRITE in the pvx code, it will INSERT a new record instead of UPDATEing the existing record ergo you get duplicate records.
There is another reason in Premium dupes can happen on reports that relates to settings in the SY_SQLOptimize.m4t file but that doesn't appear to be related to this issue.