Ground Speed can only be measured relative to - and at - the ground. The surface. Terra Firma.
If it takes 5 hours to fly from directly above point A on the ground to directly above point B on the ground, and A-B is 1000 nm, then the ground speed was 200 kts. Period. It does not matter whether the trip was made at ground level or FL320 or in a low earth orbit of 320 nm.
One's actual speed through the Universe or through the "ether" may have to be higher at FL320 or 320 nm than at the ground, due to flying an arc following the curvature of the Earth at a wider radius (or fighting heavier headwinds, or no significant atmosphere at all) - but actual speed is not Ground Speed.
It is possible an E6-B or GPS or other calculator does not take into account that wider radius (and thus longer distance at altitude) so it may not tell you the correct IAS or CAS to fly to achieve a given ground speed, or it may display an inaccurate calculated (as opposed to actual) Ground Speed. But that is an error in the calculation algorithm - not a "higher" or "lower" ground speed itself needed to cover a given ground track in a given time.