What would overriding an instance variable mean? I just don't think it would make sense. There's no "implementation" to override. If an instance variable is private then subclasses can't access it anyway, and if it isn't subclasses can just use it.
If the Java language designers let us overridden the instance variable then the instance variable need to be declared with any access modifier rather than private which will break a fundamental principle of object oriented programming, i.e., encapsulation. But, we can override the properties method in the subclasses as follows: