פירוש על עבודה זרה 63:7

The Talmud responds by taking note of a contradiction between the two halves of the baraita. The first half allows one to sell earthenware flasks belonging to non-Jews even though there is wine absorbed in the flask. Assumedly this is permitted because the Jew is benefiting from the flask and not the wine absorbed in it. The second half prohibits using the leather flask for any use whatsoever, even if the Jew does not care about the wine and wishes to use only the leather.

Rava explains that in the second half of the baraita the issue is not directly deriving benefit from the leather flask with non-Jewish wine in it. If this were the only issue, the act would be permitted. The problem is that he might use this leather to close his own flask. Should he do so, he might come to mix his own wine with the non-Jewish wine, and this is prohibited. In contrast, there does not seem to be such fear when it comes to using Hadrianic earthenware to support the bed.