פירוש על עבודה זרה 111:4

The baraita states that even though he has skimmed the waste off of the wine that it is in the vat, he may still drink untithed liquid that comes from the press, which is above the vat. Clearly this baraita considers the skimming that occurs in the vat to be the skimming that makes it liable for tithes and subject to yayin nesekh.