save all isn't necessary but

when you have the page with all settings, if you for error change one or more options (radio option)
and you not click the button "save all", the modified remain;
this isn't good because is always better a botton for confirm the new settings;

I think one solutions can also to be a Botton(or Check) Option that run by default a javascript code that cicle all radios (and checks) options and make them unselectable;
so one must first activate this Botton/Check option for to change options settings.