I think that height only is a measurement that tends to mislead. I am 183 centimeters but have long legs for my size but short arms. Almost every time someone gives me a suggestion for a bike it results in extreme discomfort for me as I am much too stretched out. It seems to rank up there with the ivory billed woodpecker for sighting bikes with a short toptube, short enough for someone with body dimensions such as I have.
My theory is that the Audax is designed with a moderately steep angle. Without checking I think it is 73 degrees. There was a bit of a flap once long ago during a magazine review of the older Audax where the journalist made a big deal about toe over lap, and I suspect that the top tube may have been left a bit long so as to minimize this possibility. Slackening the head tube angle would change the handling, slowing it down a bit (which I would have liked). I always look at two things first when I consider a new bike. A very short reach versus stack, if the maker publishes that figure, and in the absence of that knowledge simply a very short top tube, and how much steerer is available on the forks.
Thorn does wonderfully on the steerer, the best there is. But the long top tube on the audax would have me looking at the 550s a size most would consider much too small based if based solely on my height. I don't care about toe-overlap one bit. But then I'm a cyclist, not a journalist looking for a tempest in a teapot.