A is A is not a redundancy, it is a tautology. In this sense, you are correct in claiming that this phrase is jejune. However, I take this phrase to mean, "An object is the sum of its observable properties and behaves, as per the Law of Causality, according to its nature. In other words, things are what they are observed to be, no more and no less. What is more, if you have a concept that cannot be reduced to anything perceivable, then your A may be any non-A you wish. Such concepts must be considered invalid.
I disagree that the definition makes A, A. Rather, the definition is used in concept formation but when our system of concepts conflicts with perception, it is perception that must rule the day. Things are not what we define them to be, they are what they are. Our definitions are mere classification schemes for percepts constructed for our own purposes.