[graup]

I think you made the same mistake that I made when I first read it. The question isn't "what contains more wine?" but "compare the amount of water in A to the amount of wine in B."

Step 1: A with 10 L wine; B with 10 L water

Step 2: A with 9 L wine; B with 11 L liquid (10 L water and 1 L wine => 10/11 water, 1/11 wine)

Step 3: A with 10/11 * 1/11 = 10/11^2 L water; B with 1/11 * 10/11 = 10/11^2 L wine.

10 / 11*2 water in A ~ 10 / 11^2 wine in B.

[daveFNbuck]

You're misunderstanding the objection. They're saying that if you move 1L of wine to the water side, the side you poured into will have fewer than 11L and when you pour 1L back the two sides won't have equal volume.