These days engineering word is used for conducting. He engineered the meeting. He engineered the show. In such a case all the organisers can also be called engineers.
Anyhow, I may be wrong in my understanding and many people may support the statement made by the author.
Now coming across the precise definition of a writer, he is definitely the planner and the executor of penning down some ideas which will enhance his status as a prolific writer. He is full of artistic skills and lacks the technical know how as expected from an engineer. Hence going through the different characteristics of his qualities, the job of the writer differers from that of an engineer. Though both are excellent planners but have the different roles needed to perform. Hence a writer cannot be defined as an engineer.
Knowledge is power.