I'm afraid I don't know what you're getting at... I'm aiming to be able to start new projects with Hardened Runtime off/disenabled (because it won't allow the SFML libraries), without having to turn it off manually each time. But my statement that non-SFML-template new projects started with Hardened Runtime off was based upon an older version of XCode, and is no longer correct. A basic XCode project, without SFML template, does start with Hardened Runtime enabled. So I suppose it has nothing to do with the SFML template.
Still, I am puzzled as to why the code I posted *doesn't* turn it off, since I'm specifying it in custom settings. As mentioned, other custom settings listed the same way do indeed take effect in my customized SFML template.