S/4HANA Material Coverage apps and Shortage logic

[Louis-Nicolas]

Dear SAP Community & MRP expert!

I am running MRP live (with Advanced planning - PP/DS) in S/4HANA 2022 FPS02 version and we are struggling to understand how does SAP works for External procurement proposal :

Here an example from Material Coverage: Requirement is for the 25.06, but the purch. Req is placed 1 days AFTER ?

Then, Material Coverage apps, request to manage this “shortage” and make a proposal to advance the Purch. Req of 1 day. Of course!  

PS : my Purch.Req is not fixed, and I am not using TimeFence. So, I am expecting the MRP live to reschedule it here automatically.

In PP/DS RRP3 we can see that the PurRqs is well scheduled …

I am struggling to understand the logic of these proposal :

1. Why does a planner should fix this kind of planning/scheduling issue ?
2. What does a Shortage is triggered in this case (I means why not automatically rescheduled)
3. Also, why does the others PurReq / DepReq for July are well scheduled  ?

Is there any master data or customizing that could influence this scheduling issue ? 

Thanks!

[Louis-Nicolas]

Up! Does someone have an answer ? Else I will open a Case to SAP...