Wasn’t manifest v3 supposed to prevent dynamically loaded code? As the article says these extensions are featured but (I think) the latest update to v3 says: “In January 2023, use of Manifest V3 will become a prerequisite for the Featured badge in the Chrome Web Store.”
No. Manifest v3's main role was to cripple ad blockers... hence you're now seeing YouTube experiment with "anti-ad-blocker" popups warning users they wouldn't able to see the site.
They know they got people by the balls after they rolled out v3 earlier this year.
Thing is, you can't load javascript code... But you can easily write a mini virtual machine to run any code you download from the web. And due to javascripts introspection abilities, that VM can (if the developer wishes) do anything.
The simplest javascript bytecode interpreter is probably only a few hundred bytes, which is easy to hide in a big extension.
https://chromeos.dev/en/posts/manifest-v-3-migration-timelin...