jaxb - 属性のみの要素のコレクションの @XmlElement が xsi:nil を出力しない

Question

私は非常に興味深い状況にあります。

public class Child {

    @XmlAttribute
    public String name;
}

@XmlRootElement
public class Parent {

    public static void main(final String[] args) throws Exception {
        final Parent parent = new Parent();
        parent.children = new ArrayList<>();
        for (int i = 0; i < 3; i++) {
            final Child child = new Child();
            child.name = Integer.toString(i);
            parent.children.add(child);
        }
        final JAXBContext context = JAXBContext.newInstance(Parent.class);
        final Marshaller marshaller = context.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE);
        marshaller.marshal(parent, System.out);
    }

    @XmlElement(name = "child", nillable = true)
    public List<Child> children;
}

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<parent>
    <child name="0"/> <!-- xsi:nil expected -->
    <child name="1"/>
    <child name="2"/>
</parent>

xsi:nil質問 1:それらに属性がないのはなぜchildrenですか?