Upgrading to rails 5

Just looking at the guide for upgrading an app to rails 5 [1], and
have a question

In section 2.2 it says the ActiveRecord models now inherit from
ApplicationRecord, so when upgrading one should create
application_record.rb containing

class ApplicationRecord < ActiveRecord::Base
  self.abstract_class = true
end

However it does not say that one should modify existing models to
derive from this class. I think this is just an omission in the docs,
is that right?

I note that in section 2.4 talking about a similar change to ActiveJob
that it /does/ say to change the base class for existing jobs.

Colin

[1] http://edgeguides.rubyonrails.org/upgrading_ruby_on_rails.html