I looked it up and my overall conclusion was that they each are generally the same size, usually weighing around 6.5 lbs. However, I’m not sure about wyandottes, but I wouldn’t be surprised if your hen is just a big australorp, as I’ve had many.
Totally random comment here, but…. Am I the only one who at first thought this was supposed to be a “ pullet project “ page, but you miss-spelled it 😅😂