Correct. Frisia (or Fryslân) is a bilingual province. Frisian is an official language of the Netherlands. Someone called in front of a judge in the north of the Netherlands has the right to be heard in Frisian, for example.
Fun fact: villages, towns, and cities in Frisia often have names which differ in Frisian and Dutch. In those cases the signs at the place limits will have both names listed; the official one on top (which in some cases is the Dutch name (e.g., Leeuwarden/Ljouwert) and in some cases the Frisian (e.g., Gytsjerk/Giekerk)).
I really like that the intercom announcement voice in our trains (and also buses?) is bilingual.
And huh interesting, I didn't know that for some places with bilingual names, the Dutch name is official and for others the Frysian is? Who gets to decide that, the municipality?
Yep, the municipality decides on such matters. Places do still occasionally have their names changed (rarely of course, because it involves a lot of work including updating addresses), usually aligning with local use. In the case of De Westereen a name from the local dialect replaced both the Dutch and Frisian names (Zwaagwesteinde and Westerein, respectively).
In a number of cases originally Frisian names actually supplanted older Dutch names (e.g., Burgum, Grou, Eastermar, etc.), so those places have just one name in both languages (except on the Dutch language Wikipedia because of weird reasoning about allowable sources and apparently a hatred of Frisianised Dutch names).
Fun fact: villages, towns, and cities in Frisia often have names which differ in Frisian and Dutch. In those cases the signs at the place limits will have both names listed; the official one on top (which in some cases is the Dutch name (e.g., Leeuwarden/Ljouwert) and in some cases the Frisian (e.g., Gytsjerk/Giekerk)).