Exhaustiveness warning for class with private constructor?

example.scala

final class Currency private (val code: String) extends AnyVal

object Currency {

  val USD: Currency = new Currency("USD")
  val EUR: Currency = new Currency("EUR")

  def from(code: String) : Option[Currency] = code match {
    case USD.code => Option(USD)
    case EUR.code => Option(EUR)
    case _ => None
  }

}

sealed abstract class Country(val code: String, val name: String)

object France extends Country("FR", "France")
object UnitedKingdom extends Country("UK", "United Kingdom")

object Country {
	
  def from(code: String): Option[Country] = code match {
    case France.code => Option(France)
    case UnitedKingdom.code => Option(UnitedKingdom)
    case _ => None
  }

}

// TESTS

// we get an exhaustiveness warning
def test2(c: Country): String = c match {
	case France => France.code
}

// we don't get an exhaustiveness warning
def test(c: Currency): String = c match {
  case Currency.USD => Currency.USD.code
}