hibernate-jpamodelgen generates no public static final String fields, only SingularAttribute/ListAttribute fields

Question

I have added the hibernate-jpamodelgen Maven dependency to my project and the metamodel classes were generated. I do not know why the metamodel classes contain no public static final String fields, only SingularAttribute/ListAttribute fields.

The relevant dependencies are

<hibernate.version>5.2.18.Final</hibernate.version>
<hibernate.javax.persistence.version>1.0.2.Final</hibernate.javax.persistence.version>
<dependency>
    <groupId>org.hibernate</groupId>
    <artifactId>hibernate-core</artifactId>
    <version>${hibernate.version}</version>
</dependency>
<dependency>
    <groupId>org.hibernate</groupId>
    <artifactId>hibernate-jpamodelgen</artifactId>
    <version>${hibernate.version}</version>
</dependency> 
<dependency>
    <groupId>org.hibernate.javax.persistence</groupId>
    <artifactId>hibernate-jpa-2.1-api</artifactId>
    <version>${hibernate.javax.persistence.version}</version>
</dependency>