The air data computer receives data about a number of things amongst which the aircraft heading and airspeed. It also receives information about the aircraft geaographical position and thus can calculate the ground speed and track. The difference between these two pieces of information can only give you the wind speed and direction.
As the track made good and gound speed when in contact with the ground the two will be the same, ie. the wind has no effect on the heading or ground speed whilst taxiing, the wind velocity wil no be shown or be spurious.
I have seen some strange displays of wind velocity whilst on the ground but this is only due to the computer's calculation and the occasional jumps in GPS position.