As a mater of fact I did.
The help window suggests that if "General" check box is checked and the filed is incomplete, subsequent functions will be blocked. However, while testing that doesn't happen. If the PO number is incomplete, I get a warning and the order goes on in completion log, yet I am able to create delivery document and invoice.
This is what I am finding extremely confusing. fields with 00 and 01 status group aren't blocking any subsequent documents. For 00 it makes sense but not for 01.
I've made sure that that I'm looking at the correct Item category - incompletion procedure - field status group assignment.