Yes, roger. But what Capt. Pit Bull is pointing out is that an aircraft at, say, FL170, maintaining 280 KIAS might be doing a very different groundspeed from another aircraft as little as 20 miles from him, also FL170, also maintaining 280 KIAS, the reason being horizontal differences in the wind. Controller sees the difference on his display and thinks "Aha! Someone is telling porky pies!". Not necessarily so.