I am using Google Maps for navigation on my wife’s phone And as you probably know. They do not have speed and speedlimits incorporated.
Then I downloaded an other app called Velociraptor. Which supplies speed and limits on any maps.
And this app uses OSM the get the speedlimits.
But the speedlimit is blank until I get about 15 km south from my house. Then it works perfectly.
So it has nothing to do with editing Google maps.