(This feature request may be considered part of #5287, but doesn't entail as much, as a single audit.)

The intrinsicsize attribute was proposed to allow developers to have images maintain aspect ratio, proportional to the width of the screen, without causing a user visible reflow.
The attribute proposal was superseded by the new UA-defined styles (Chrome status):

img, video {
    aspect-ratio: attr(width) / attr(height);
} 

The WHATWG HTML spec is also to recommend developers to set width and height attributes (specifically for images, when lazy-loading), however most developers usually don't seek information in the spec and so an audit would increase the likelyhood that developers gets exposed to this recommendation.

As a side note, I think it's important that developers don't disable scroll anchoring by setting (or inheriting) overflow-anchor: none.

Thanks for taking your time.