This thread is about Apple servers accessing the contents. Of course the OS has access to the contents of your messages, how else do you expect it to show a preview of the message? Do you want each notification to be a custom-rendered widget from the app?

If the contents are that sensitive you must disable the preview. Even then, the OS has access to the pixels in your app so it really is a moot point.

The caching issue here was evidently a bug.