Why would it even have that feature.
The entire point of robot cars is to create safety by removing the chaotic lawlessness of humans.
At some point, if we reach 99% saturation of autodriving cars, we can revisit raising speed limits.
I mean it probably has that feature so the car is driveable and useful in that mode? If it always drove at the speed limit you’d be a huge traffic nuisance, at least in America – maybe European speed limits are better set