I don't get this at all. You seem to allude that the "native app data sandbox" gives some sort of security or privacy not possible in a webapp, but webapps are

I don't get this at all. You seem to allude that the "native app data sandbox" gives some sort of security or privacy not possible in a webapp, but webapps are restricted by default, able to run without being installed on your system and are run in a much stricter sandbox than a native app is. If you value privacy and security I don't see anything that would favor a native app over a webapp. I do understand the performance and native integration arguments for a native app, but saying a native app by definition offers more privacy or security seems odd.