Why is withUnsafePointer using a new pointer (or different pointers)?

Question

Consider the following:

class MyClass {
    private static let c = MyClass()

    func shared() -> MyClass {
        return MyClass.c
    }
}

var a = MyClass().shared()
var b = MyClass().shared()

let message = a === b ? "same instance" : "different instance"
print(message) // "same instance"

withUnsafePointer(to: &a) {
    print("a: \($0)") // 0x0000000119dfcc18
}
withUnsafePointer(to: &b) {
    print("a: \($0)") // 0x0000000110abcc20
}

I would have expected the pointers to be the same. Why are the pointers different?