When I started development 15" monitors were standard and 17" were a luxury. Setting multiple monitors was a must or you would have to constantly switch between editor, terminal and documentation.
If you look at the setup that's exactly what is happening. On a single screen there is browser with documentation (presumably), and there is four (!) IDE/editor/terminal windows.
It's not about how many monitors you have but rather what you are doing with them. You can put Netflix as one of the windows and still get distracted on a single monitor setup or you can have bad sight like me and require two 27" monitors side by side so that I can magnify fonts and have documentation, IDE and terminal at the same time with no strain.