Do you actually have any reason to think it reads notification contents? This feature has never done anything that made me think it is. (genuine question, I’m in the EU and we don’t have Apple Intelligence here)
2. "Show content in Search", uses Apple Spotlight to index all app data. For an E2EE messenger, that is not only notifications, but all text/image/audio data in message history.
As stated at the top of this subthread, these menu options preceded Apple Intelligence by several years. Implementation would have changed over time.
