Say you have a long page that lists “Pre-existing conditions” at the bottom, and near that section is also a unique image or other external asset. If you click on the link and cancer is in your list, the page will scroll and load the related assets instantly. Without cancer in your list, you’d only load those assets through human scroll, which would most likely look different timing-wise. Thus you can determine with high probability whether your target has cancer listed (if you have access to DNS records, as mentioned in the example, and the target is using a browser that delays offscreen asset loading - like this same latest Chrome).

Whereas anchors tend to be generic (#preexisting-conditions), this new scroll behavior can be used to create an existence check for any user-specific text on the page (in carefully crafted scenarios). There are probably other variations that could be devised on this concept, since it allows indirect page interaction that can bypass authorization walls (since the browser would transmit cookies normally and such).