Even Kurama got confused over Madara and the Fake Obito, when he appeared to capture Naruto. That was when Kurama assisted naruto willingly in battle, stating he hates madara more, though it was in reality Obito faking as Madara.
Sasuke has never met madara before. If Kurama, who has been possessed by Madara, knows his signature Chakra, and still mistakes Obito as Madara, then What can Sasuke know about who Madara was or How would he be ?
Also, it may have been forbidden to talk of madara in the village. As you know, all were forbidden by III hokage not to talk about nine tails and naruto. similarly, II hokage might have forbidden all not to talk about Madara, other than that he was killed by the God of Shinobi, the I Hokage.
