IOS Holliday calendar in wrong language

I’m living in Belgium, where half of the population speaks Dutch and the other half speaks French (and a minority speaks German). But it is not the only country in the world with multiple languages, so this must be a common problem.

i’m Dutch speaking but I prefer running my Operating Systems in English. So my iOS is running in English, but my region is set to Belgium. And in my preferred languages Dutch is placed before French.

But in the Calendar settings I selected Dutch for the App language.

But in calendar selection of the Calendar app I still get the Belgian Holliday calendar in French instead Dutch.

If I put iOS in Dutch I get the correct Holliday calendar, but I don’t want to do that. The preferred language order or the app language should make it easier to select the correct Holliday calendar.

Of course a language selection in the region selection would be ideal, like we have in windows.

Can this be corrected ?

Thanks.