In The feed role , "Authors MAY use heading and separator children in a feed . For example, in a feed of news stories there could be headings separating sets of articles into sequential dates. If a feed does have headings or separators as children, they SHOULD NOT be focusable or contain information necessary for understanding or navigating the feed 's articles ."

Confused with last sentence "If a feed does have headings or separators as children, they SHOULD NOT be focusable or contain information necessary for understanding or navigating the feed 's articles ". May be provide examples like timestamp and name etc. Provide some explicit info

Also, will there be any related info is added to the heading and the separator role?

Should we consider adding the scrollbar role as an allowed child element?

When dealing with a high but "static" number of articles, showing them on scroll for any reason (e.g. for performance reasons), this setup might be one of the rare cases where an author would want to create a custom scrollbar.
By doing so, it would give the impression that all the content is already fully loaded, allowing users to see the entire scroll progress right from the initial page load.

I understand that the scrollbar can be positioned outside the feed element, but I don't see why the author shouldn't be allowed to place it inside, as the scrollbar is an integral part of the feed document.

Regarding the rest of the addition, I like it. The details about focusability and not including important text are crucial for maintaining a smooth experience for keyboard users.