Yes, that is a legitimate Finland personally have had similar device before the actual trailer acquisition
but Finland maximum road speed towing is merely 60kmh because it is towed device and so it is not trailer what may tow 80kmh
I've heard a nickname "dolly" for those.
Besides the speed limit the car being towed must have valid licence plates on it. This makes a difference for pure track/racing cars that are not registered. Transporting them on a trailer is fully legal (of course).