This feature preserves the sticky user activation state after a page navigates to another same-origin page. The lack of user activation in the post-navigation page prevents some use cases like showing virtual keyboards on auto-focus, and this has been a blocker for the developers who want to build Multi-page Applications (MPAs) over Single-page Applications (SPAs). Note that browser-initiated navigation requests (reload, history navigation, typed URL in address bar etc) are not covered by this feature.
Samples: https://vmpstr.github.io/htmldemos/activation/a.html