He didn't explain HOW "HTML5 videos are more searchable and indexable." Is there an attribute or property that search engines pick up that isn't available when

He didn't explain HOW "HTML5 videos are more searchable and indexable." Is there an attribute or property that search engines pick up that isn't available when you embed flash? A lot of the best additions in HTML5 are in the DOM. Search engines don't run JavaScripts so it doesn't seem like HTML5 adds much in the way of on-page optimization. Maybe the new section tags will have a benefit but this article wasn't about those tags.