I read your comment and thought that was a ridiculously tight margin of error, even for the Germans. Then I looked up the fine.
€15 for an in-town violation, €10 for out-of-town, no points for less than a 20 km/h variation? That's more of a secret tax than an actual deterrent.
Electric cars can't regulate the speed more smoothly than gas cars while on cruise control. It's about the control algorithms, not the source of power, and the gas systems could be on tighter control ranges if it weren't so inefficient and uncomfortable for the passengers. Adaptive cruise control runs on a PID loop control scheme and overshoot is inherently part of the game.
While on cruise control a car will go slightly faster than the speed setpoint for a few seconds, then slower, then faster, until it settles on exactly the correct speed. Then you go down a hill and it takes a little while to slow down, or you go up a hill and it takes a little while to speed up. Electric cars can use regenerative braking when the car is going down a hill but they're still constrained by the nature of control loops and aggressive braking will just lead to wonky acceleration-braking cycles while hunting for the setpoint.
That's also how humans drive. We just don't do it as well. If you're worried about tickets set your cruise for 3 km/h under the posted speed.
The setpoint is the setpoint. Key element of controls engineering. Secretly subtracting from the setpoint behind the scenes to compensate for your local driving laws would be the car lying to you and just leads to more trouble than it's worth.
Every day people tell me that they want a setpoint to be the temperature that the room never exceeds or the temperature it never falls under or five degrees above the highest temperature the boiler hits. It's like setting your clock ahead by five minutes to avoid being late. You can do it if you want to but it's ridiculous functionality to build into the timepiece.
Further, outside of detection errors like the one in this article, the reaction time of a self-driving car is orders of magnitudes faster than a human. You don't need 5m more braking distance per 5km/h because within milliseconds of the computer noticing the issue the car will hit the brakes. Human reaction time is more like 0.7s to 3s. You still need more time to brake as you go faster but the computer doesn't need as much time as our human laws already give us.
In a case like this where the victim enters the path of the car closer than the car's brakes are capable of stopping, even given instant detection, a human would have just hit the victim at a much faster speed because of the reaction time. That's going to happen sometimes. It's just how it works.
Basically everything you're saying is based on an outdated notion of how cars work and in particular your very German desire to follow the rules exactly. The rules are going to change, dude, and in the meantime you're free to set your cruise at 47 km/h to avoid accidentally triggering a photo-radar trap if you like.