[codeddesign]

It's called "outstream" video ads. (instream would be a pre-roll where it plays over another video you are wanting to watch)

The publisher has not control over this and probably doesn't realize it's happening, it's purely the 3rd party ad provider they are using that is controlling that.

There are standards in which most ad companies follow (user must be 25% in view, ads must be muted...etc), but recently a large number of Israeli based ad firms have begun running outstream ads without these standards. The purpose is to drive up the view and completion rates. This gives them access to larger media buyers and higher fill rates (filling video ads for every page load is very hard to achieve)

Reference: years of being in the video ad industry