It seems you are right: https://www.magicearth.com/faq/#traffic-and-events-help

Where do you get the traffic and road closure info from?

We get it from a third-party provider; it is not created by us.

It’s limited to mostly first world countries: https://www.magicearth.com/feature-availablity/#hd_traffic

But somehow, someone tracking it’s users, I can’t imagine other way to get data like this. Maybe some carsharing service, company fleet management or something like that.