It's not clear what the field "WBS Element Is Statistical" means in App Projects - Plan/Actuals
SAP S/4HANA Cloud
Reproducing the Issue
Start App Projects - Plan/Actuals and check the field WBS Element Is Statistical
"WBS Element Is Stat." is the flag indicating whether the posting was done as "real" or "statistical".
For some of the postings the real object where the costs are booked to is another object than WBS element. Then the "real" posting is performed for the real cost object and the posting to WBS Element is considered as "statistical".
You can check the field "Account Assignment" with App Journal Entry Analyzer to identify the real object for the posting document.
Stat, cost report, X, #, FI document, accounting document, ACDOCA, ACDOCP , KBA , CO-OM-IS , Information System, iViews , PS-COS , Costs , Problem