I was specific in mentioning the Comp, not the Pro that you linked too. The Comp, possibly as an error on the Specialized website, indicates the same HTA and STA across sizes. I would actually suspect the angles as indicated on the Pro are the correct for the Comp as well, seems like an error on the website.

I would have to call Specialized to confirm whatever STA's the 56 sized Comp has, as that's the size I would fit on. As I have never ridden a road bike with such a steep angled seat tube, I would likely pass on this. I have a Spec. mt bike that uses steeper seat tubes, 75 deg. is common, that climbs well but you do feel a bit forced forward to the bar.

In fact, as I look further on the Spec. website and look at Aethos Comp equipped with SRAM, the STA and HTA are both 73.5. Which I suspect is the correct dimensions for the 105 Di2 bike as well. Seems like typos on the website,