Huh. Learn something new every day.
A whole bunch of people block the use of browser devtools, by (for example) killing off page content when it's been detected.
I've just come across one that kills the site as soon as the inner window width is 200px less wide than the outer - but that also kills a site for any users of tabs going down the side instead across the top of a window.
Hm! Not seen it before.