[ts330]

I suspect this will lead to ads not being served via the site's code own code, but rather by Chrome overlaying the ads into the site using placeholders defined by the site.

By controlling the ad experience at this level (and this possibly being the only way to avoid being blocked), Google can enforce an ad-experience that is akin to in-feed facebook ads.

It also provides a far greater level of security around the ad unit and a far better level of accurate targeting (cookies don't get used, your login does). These two things together provide a new way to interact / monetise those ad units.