It's just due to the resolution of his monitor. The higher the resolution the smaller the design will appear on screen.
Ahh, think I was misreading what he wanted

I tested this on a 3440x1440p, and JSP does have a max width of 1900. I manually set it to 3440 in the second picture which you can do temporarily in the dev console. To do it permanently you would need something like tampermonkey and a custom script made though. Both same zoom % as well so not sure if this is what you're looking for?
Native JSP

JSP set to 3440 width
