100% in Photoshop has nothing to do with physical size. It means that one image pixel is represented by exactly one screen pixel. The size on screen depends on the actual screen pixel density, whatever it happens to be.
Consumer-oriented image viewers don't have to display accurately. They will usually scale the image according to the scaling set in the operating system, something Photoshop will never do because it has to display the pixels accurately. So if Windows scaling is set to, say, 125%, Windows Photos will also scale the image up to 125%.