They could also, with a breaking change, enforce addons register what sorts of files they'll execute when a folder is opened in trusted mode. If no matching files are found, then opening the folder is safe and no prompt is needed. If matching files are found, then prompt the user and replace "may" with "will". Fewer permission requests, and a clearer message.

People will still inevitably ignore the message and open everything in trusted mode, but it'd be more reasonable to consider that user error.