Another interpretation to "binding senjutsu" would be Sasuke absorbing Madara's senjutsu chakra (trapping the chakra inside himself). Orochimaru refered to the word "Senjutsu" as Senjutsu chakra.
In the other hand, binding Madara is to stop him, paralize him, trapping him, or anything alike. And, "in response to that" would be that the catalyst for this jutsu to take effect would be Madara using senjutsu chakra. So, semantically, "binding him" and "binding senjutsu chakra" are not the same... assuming the same would be mistaking cause by effect.