This is brilliant. I hope we see more countries doing the same thing :)
Maybe they could make accounts be tied to residency or citizenship, and perhaps have communities that only allow posting to those accounts to reduce bot spam and foreign meddling. Maybe that's a terrible idea, but it will be interesting to see where this goes, and if activity pub will be sufficient or need extending.
If I understood this correct from my interpretation of the dutch server description this is an Instance for dutch government officials.
At least Germany also has such a mastodon instance too for quite a while now. So people on mastodon know that an account there is officially a government account. The BSI (German Office for cyber security) and other offices post there.
This is not an Instance for "normal people" to register on.