It’s the opposite. If you pause the video you the viewers are almost always looking at the screen. The pause button on a mobile phone or web browser is literally on the player. You are guaranteed to see it immediately after you push the button. You will see it when you un pause. These ads are display banners not video. It only takes a second to see the ad.
Unlike video ads that just auto play, especially when the video player auto plays more videos, there probably is more probability you aren’t actually watching, unlike pause ads that require user activity and focus on the screen to push the pause button.
YouTube wants you to keep watching the videos. The more time you spend on the site the more ads you see. They care about finding the balance of acceptable ad load to maximize ad space, which requires a consistent user base. I have faith that this is their objective. Also, videos take time to load and a user hitting pause is unpredictable. A light weight display ad is probably the best technically feasible way to grab a user’s attention in that brief moment of hitting pause. Especially when pause means a user wants to mute audio to do things like take a phone call, a video would turn off users to the platform.