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You are right that it is perfectly possible to do this with topics. The best argument for this is that the actionlib completely relies on topics for communication. For every action, a set of topics (e.g. for goal, feedback and result) are created and handled internally so that the user can concentrate on the fun part and does not have to care about the internals.

The book does only talk about actions in the move_base example on p. 269ff, ('action' is not even listed in the index!) which is imho a red flag for a book about ROS. So you are right and the part you quoted is simply wrong.

"The services are developed by the user, and standard services don't exist for nodes." std_srvs...

"The files with the source code of the messages are stored in the srv folder" At least inaccurate, the srv contains the foo.srv-files which are used to generate the source code (which is never put into the srv-folder)

You are right that it is perfectly possible to do this with topics. The best argument for this is that the actionlib completely relies on topics for communication. For every action, a set of topics (e.g. for goal, feedback and result) are created and handled internally so that the user can concentrate on the fun part and does not have to care about the internals.

The book does only talk about actions in the move_base example on p. 269ff, ('action' is not even listed in the index!) which is imho a red flag for a book about ROS. So you are right and the part you quoted is simply wrong. wrong.