I dunno about the situation with the languages of Italy, from a cursory glance at Wikipedia it seems a _lot_ more complicated than Frysian/Dutch in NL, so I really don't think it's anything "like saying" that.
But "official" means exactly what it means, and when I'm saying "Frysian is an official language of the Netherlands", it means that it's recognized as an official language of Netherlands, by the Dutch government. And if it was up to the provinces I dunno, but it's not. Frysian is the one that's considered one of the official languages of the Netherlands.
I also don't think comparing to Italy makes sense at all because countries are different and decide what are their official languages for very different historical reasons. For instance you can look up what Dutch government body is responsible for deciding the Frysian language is an official one in the Netherlands and why, and you will very likely find no Italian equivalent of that.
It's not really that difficult, an official language OF a country is recognized at a national level. Thus all official government communication must be issued in that language. In the Netherlands, only Dutch has that level of recognition. Same in Italy for Italian
Then there are other, regionally-rocognized language that local governments use alongside the national one (West Frysian in Friesland, German in South Tyrol, etc.), and may even enjoy a majority of speakers within those regions, but they are not "an official language OF" the wider country.
