I got both BR and Aussies from McM last summer and this little one looks like it could be either. The Aussies had white on them like this and some of them had light colored beaks and feet that by 8-weeks had turned the slate colored as they should be. The rocks were in a separate batch from the Aussies, but if I had ordered them together would not have seen any difference for a few days.
I still don't see how anyone can distinguish gender at a day or two old by a picture unless it were some sort of sex-linked color difference, which I just don't see here.
Time will tell in both respects.
BUT DON'T get hung up on it being rare. Like I said before, they don't really give you rare all the time, it is just a free chick of their choosing from whatever they have a lot of.