Hi Jiro,
Since your material is on Standard Price, it will create the accounting document no matter what, whether you use 561 or 511 only thing is it will credit revenue from price difference account.
One thing though, if its initial Upload and you want to upload the balances for the first time, then what you can do is DO NOT enter price in accounting view of material and upload using 561 and it will not create the accounting document.
But if its in the middle of operation already and your material is Standard price it will, this is standard behavior of SAP.
Khurram