SwiftData: Default value for added property

Let's say I have a model like this:

@Model
final class DataModel {
    var firstProperty: String = ""
}

Later on I create a new property as such:

@Model
final class DataModel {
    
    enum DataEnum {
        case dataCase
    }
    
    var firstProperty: String = ""
    var secondProperty: DataEnum? = .dataCase
}

My expectation is for the data that is already stored, the secondProperty would be added with a default value of .dataCase. However, it's being set to nil instead. I could have sworn it would set to the default value given to it. Has that changed, or has it always been this way? Does this require a migration plan?