This is more-so related to the associated event for content-visibility: auto (i.e. contentvisibilityautostatechange). I noticed that in Chrome (131) this bubbles, while in Safari (18.1) and Firefox (133) it does not. I was planning on making a WPT for this, but I don’t really know what the behaviour should be, so I figured I’d ask here. The relevant section in the spec mentions nothing about bubbling.

I made a demo highlighting the bubbling problem.