Controllers are only presented with ground speed on a surveillance display. That is what they and aircrew use for time/distance. To know what airspeed is they would need a readout from the acft ASI. They may, for instance, ask for the acft IAS when applying speed control between acft. E.g. when one acft is following another, they may request the IAS of the lead aircraft and then instruct the following acft to fly at, or not above, that speed to maintain separation.