Mac: Function keys can be used without clicking the Fn key first

On Mac Function keys can be used without clicking the Fn key first, there is an option/setting in the keyboard preferences as below: "Use F1/F2, etc keys as standard function keys" - un-checking this will allow to use the function keys without needing to press the "fn" key.

So for ex: Within an application (I am using Eclipse eclipse.org) I can press "Ctrl+F6" instead of "Ctrl+Fn+F6". But with the keychron keyboard only "Ctrl+Fn+F6" works and not "Ctrl+F6" irrespective of standard function keys settings.