I generally agree with your statements about “adaptive/responsive design”, and I too work on desktop and laptop computers. However, I just had a look at https://www.usro.net/ and I did not have the same experience as you. It displayed perfectly fine and readable, as expected, on an 18″ monitor.
It sounds to me like the website’s CSS did not load for you for some reason. That can cause the kind of magnified spread display that you encountered. Or perhaps there was a server problem when you visited and it has been corrected now.