You cannot have a ground wind display unless you have a windvane sticking above the aeroplane (and then you'd need to allow for the groundspeed)! I am not sure when the wind vector becomes 'live', but whilst the wheels are tracking the ground, there is no way the system can detect any sideways drift to assess the wind. I'm never looking down there and neither should anybody else on take off or landing! You always have a simple groundspeed display. If there was a 50 kt wind across the runway, the FMS would have no way of knowing until the wheels lifted off and the aeroplane started being blown sideways.