We used to listen to at the document level for this event. That allowed us to listen to up/down arrow key events while another section
of DevTools (like the search input) was focused. This was a minor UX positive.
(We had to use ownerDocument rather than document for this, because the DevTools extension renders the Components and Profiler tabs into portals.)
This approach caused a problem though: it meant that a react-devtools-inline instance could steal (and prevent/block) keyboard events from other JavaScript on the page– which could even include other react-devtools-inline instances. This is a potential major UX negative.
Given the above trade offs, we now listen on the root of the Tree itself.