Since we'd still have to inspect the properties to determine the default value, I'd leave it for now. `+storageBehaviorFor<Key>:` implementations would most likely contain a single return so I don't think subclasses would gain a lot by separating the overrides into multiple methods (unlike the more logic intensive merge operations for example.)

I'm all for revisiting this if it comes up in the future. Since that change wouldn't break any compatibility, it could be introduced in `2.x`, too.