No, they don't. The browser accesses the content directly from the website, and currently stores it in a cache folder on the user's computer. (The caching step

No, they don't. The browser accesses the content directly from the website, and currently stores it in a cache folder on the user's computer. (The caching step isn't necessary but eliminates the need to re-download portions of the content.) Youtube-dl accesses the content from the cache directory after the browser has cached the content.