Hi Mathieu,
I made exactly the same query in Webi and checked the SQL directly against the database. I used the ranking part and made it a standard filter in the universe. Then I applied the standard filter against the QAAWS and it gave exactly the same output.
You are right about the aggregated property, it is used inside the Webi report. But if you use the SUM-function around the object the Webi report will still act the same and QAAWS will report exactly the same. Due to the SUM-function a GROUP BY clause will be used and generate only aggregated data and therefore less rows.
About the rank by date, we just use the option “desc” to give the last date the highest ranking and then select the highest ranking. Ranking by MIN(date) is not what we want.
See also https://bobj-board.org/t/148411/14
Kind regards Armie
armie 
(BOB member since 2010-02-17)