Not quite true; historically most (i.e. official) defaulted to safe=false. Also safe=true only makes sure the server acknowledged your write; writeconcern all

Not quite true; historically most (i.e. official) defaulted to safe=false. Also safe=true only makes sure the server acknowledged your write; writeconcern allows you to wait for it to be written to the journal or more. Also, journalling is not controllable via client drivers, only via startup flags / config options.