Safari windows across two displays respond to Control and Command keypresses

This is a strange behaviour/bug which doesn't affect usability but I have noticed across several versions of Safari.

I have two monitors connected to my Mac mini. If I have a Safari window open on each display, I notice that if I press the Control (Display a Menu) or Command (I have set up as "Open <link> in New Tab") then the status bar of both the active and non-active window registers. I also sometimes get highlighting or other UI changes on the non-active monitor. The non-active window seems to be reacting to the position of the cursor on my active monitor as if it was on the inactive one.

Quite hard to explain!

It doesn't actually cause anything to be activated on the inactive window (such as opening a context menu or opening a new tab). I just catch it in my peripheral vision sometimes.

Just thought I'd raise it as an interesting quirk and wonder if anyone else has noticed this.