Yabe tutorial (1.0.2.1): different Post model in chapter 7?

I found an inconsistency in Yabe tutorial.

Code of the Post model in chapter 2:

@OneToMany(mappedBy="post", cascade=CascadeType.ALL)
public List<Comment> comments;

Code of the Post model in chapter 6:

@ManyToMany(cascade=CascadeType.PERSIST)
public Set<Tag> tags;

Now, code of the Post model in chapter 7:

@OneToMany(mappedBy="post", cascade=CascadeType.ALL)
public List<Comment> comments = new ArrayList();

@ManyToMany(cascade=CascadeType.ALL)
public Set<Tag> tags = new HashSet();

It's not the same code and there's no explanation about this change. Or I probably need new glasses :)