Kakashi was the one that said that in part 1. The majority don't believe wtf he says. He also said that the Rinnegan was a Mutation and the So6p was a myth.
Kakashi is just a smart a** who needs to e`s.
Rinnegan reads more then the MS. MS reads more then a Full Sharingan.
Does it read the whole thing? Maybe... But Madara stated the Rinnegan reads what the other eyes do and more. Its most likely the whole thing though.