I think this is more a function of the browser reporting things poorly in the header. Perhaps some client side javascript can help here?

My multi monitor setup reports even wilder results: https://aboutmybrowser.com/1708443426

It does the same thing for me - i'm browsing on my primary monitor, but it reports the resolution of my leftmost monitor. I'm guessing there isn't much that can be done other than file a bug report with whoever makes your browser.