The requirement isn't as strict as i expected. I wonder how will the maintainer handle low effort AI generated plugin that barely work.
With those disclaimers, in the the website and the guidelines itself, it looks like it'll not be an extensive review.
My best bet is those are just added to play safe in case one malicious third-party extension made it in the list.
But they'll probably do a thorough review.
If not, purely based from the context, just some tests if it's functional.
Quotes:
Disclaimer: Plugins marked as External are developed by third-party authors and are not reviewed or endorsed by the Electrum developers. Use them at your own risk. Always verify the source code before installing external plugins.
External plugins are not endorsed — Listing here does not imply review or endorsement by the Electrum developers