Work Task - Pre Accounting - Mandatory

Hello,  App10 UPD13  IEE

We want mandatory pre-posting for a Work Task code part.  We have set:

T57 (Pre Accounting Work Task)  --  Code Part “C”  --  C58 (Mandatory Pre Posting)  --  no Dft

However IFS never “stops” for the pre accounting mandatory entry.  When is (should) the requirement be triggered?  I’d assume at Task Release; but no - WT goes to Released and transactions are allowed (Issue material, report time, etc.).  Is this a possible bug or am I missing something?  Thanks