I can see how cursor movement has to be monitored to determine if it has moved to the search box or to somewhere else; in which case, you want it to disappear. But from what I've tried, it's hit and miss. Sometimes moving quickly works and sometimes if you can get to the text box within the search box in one quick movement it works as well. That's the behavior on this page as I type this reply. I'm using Microsoft Edge as my browser. That could make a difference. Maybe that's why they called it the edge.