I did not point to him being a senior engineer at FAANG, I pointed to him mentioning that he's a senior engineer at FAANG, as evidence that the book is marketed towards people who also want to become senior engineers at FAANG.

As mentioned in my original comment, I fully realize that plenty of people couldn't care less about becoming senior engineers at FAANG, and am not making any claims about the intelligence or qualifications of the author or the quality of the book.