Not necessarily against the idea but 20kph is very slow. It would be super easy to accidentally go over the limit unless you have a cycling computer attached to the bike and constantly monitor your speed.
The exact same argument can be made for cars. Doesn't stop the government wasting half my Saturday and stealing £100 every couple of years. We should congratulate cyclist on becoming fully fledged (oppressed) road users.
20kph is not a difficult speed for an adult on a push bike on a flat surface, so we’re not just talking about ebikes where a mandatory speedometer could make sense