Login intro stops polling the background once the cover is gone
A change merged into quattro stops the background intro's frame poll when the cover and the theme transition are gone, including after startup drops the cover.
After a login intro hands the background back, the shell can keep starting a status command every 16 ms for the rest of the session. The poll starts while the background is covered, and only some theme paths stop it. Finishing startup, and the startup fallback, drop the cover without stopping the poll. On a still wallpaper the status command never reports a video frame, so nothing ends it.
The timer stops itself on a tick that finds no cover and no theme transition. The pull request measured a Snapdragon X1 laptop on the stock still wallpaper, idle at 25% brightness, with and without a loop of that status command every 16 ms. Battery power was 3.27 W with the loop and 2.89 W without it.