In Finland, it is still correct to treat V and W as equivalent when sorting (e.g. phonebooks). This applies both to Swedish and Finnish language and context. However, now it is more common to treat them as separate letters, which is also accepted.

(Finland is bilingual, and the characters sets, keyboards and sorting rules are same both for Finnish and Swedish.)

In Persian, the same letter makes the oh/oo sound and the v sound. Weird.

That's because in the Arabic script, from which the modern Persian script is derived, doesn't differentiate between vowels sounds like oo/oh and their related semivowels.

In Arabic, oo and v are both bilabial sounds (produced using both lips). In Persian, v is pronounced more labio-dentally (bottom lip, top teeth), which is perhaps what causes the confusion.

But the lack of written distinction for these sounds is common in many scripts including Indian, Greek, and older Latin.