Sasuke did learn that Tobi's not Madara.
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Kirin Rei used to do better translations of each chapter. I think most of us trust her (his?) translations. Especially since this specific chapter had really crappy translations...
Or here's the copy-paste of the specific dialogue:
"*
Sasuke uses Genjutsu*
Zetsu - This is war... Defeat... Enemy...
Sasuke - That Tobi guy... He seems to be a fraud...
Zetsu - Killer Bee... Uzumaki Naruto... Capture..."
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It does make sense because Sasuke's been talking about Tobi and Madara as two separate people for awhile, and that was the only panel in which Sasuke got intel from Tobi's side.