It hides amounts in that it allows an individual user to include many inputs all registered from different identifies, without allowing the coordinator to know those inputs are owned by the same user, and then specify outputs which total the same as the sum of all their inputs. It doesn't blind inputs in such a way that the coordinator can not still see which inputs are being used. And even if it did blind inputs completely during the registration phase, at some point they must be unblinded in order to create the final transaction, at which point they are vulnerable to surveillance and censorship.