> (For human languages, governments often push towards splitting. “A language is a dialect with an army”)

Goes both ways. Nationalists often push towards lumping language varieties spoken inside the country (e.g. calling Low German "German" and not a variety of Dutch); sometimes they also split with the variety spoken in another country (calling Dutch "Dutch" and not a variety of German).

Note: I don't mean to imply anything about the current governments of Germany or the Netherlands, but more about the time around the formation of Dutch and German national identities.