As I understand it some of the cars are newer cars electrically modified (usually the previous family car, often a station wagon). Those are mostly wasteful by driving at slow speed with only two seats and no storage (which are also rules to be able to convert them). These can be converted back to a normal car when the driver turns 18 and gets a proper driver's license. But it is also possible to disable the electronic limits. Other cars are pemanantly converted much older cars and sold as such. These are the ones that are also bad cars without the regulation affecting a normal car.

Edit: Someone infamously converted and registered a heavy truck this way. Legal to drive as a 15-year-old with a moped license.

https://www.expressen.se/nyheter/eddie-15-har-en-lastbil-som...