Hope your are doing will.
I have the following case :
When creating a planned production order for an item manually , the system creates an automatic planned production order for the raw material in the produced item formula.
note that the raw material is available at the stock with quantities more than required to produce the finished items.
Can you explain to me the reason for this?
Why would you create a manual planned production order, either create one or do not as the next MRP run will delete it unless you set the status to approved - but if the system is not generating it why are you doing it?
What happens if you firm it? Is the BOM pegged supply on the line? What happens if they system created the plan?
You would probably need to look at the code, I am unsure why it would create a linked sub-production at creation, but I am not sure manually creating planned orders is a concept Microsoft really planned for.