Hi Raghu
I don't understand why you say that one input to multiple IDocs is not multi-mapping.
As documented in the following SAP Help link, a 1-n transformation is a multi-mapping.
Multi-Mappings - Managing Services in the Enterprise Services Repository - SAP Library
As I mentioned in my earlier reply, the changing occurrence XSD is a workaround from the days of XI3.0/PI7.0. Back then, the IDoc adapter does not support child messages generated out of multi-mapping. As of PI7.11 (at least), that workaround is no longer required, just a changing of the target occurrence will suffice. This has helped reduce the additional steps for developers when doing a 1-n IDoc mapping.
Unfortunately, in most places I have been the common misconception and practice from the old days are still around. I try as best as I can to inform them that this is no longer required.
I would suggest that you try it out in your system. Wouldn't saving a few unnecessary steps help in one's productivity?
Rgds
Eng Swee