RE: Use of "Doc. No. Is Prod. Order No." in Mfg Setup ?
Hi Manish,
The MSDN article you've linked to actually does a pretty good job of explaining the purpose of this field.
Still, let me elaborate:
As a user, it does not change how you use the Manufacturing module per se, but enabling this option on the Manufacturing Setup ensures that when you are chasing down Item Ledger Entries, it will be easy to find entries that have came about from Production Orders (such as consumption postings). This is because the Released Production Order No. is used as the value for the Document No. field in the Item Ledger Entry record.
If you don't check this field, you'll spend a little more time chasing the link between an Item Ledger Entry and its source Production Order (likely using the Navigate function).
I hope this helps!