So you're saying someone decides to dedicate their lives to reducing the impact of religion on the world and then honesty just compels them to write in a way that is optimized for signalling the intelligence and status of their community rather than reducing the impact of religion?

Huh? They decide to write the book in order to reduce the impact of religion. The fact that the book is specifically atheist rather than "secularized theism/ agnostic spirituality" happens because they are atheist and being honest about their beliefs.

It is far from unlikely that someone who writes an anti-religion book and is an atheist would write the book from an atheist perspective rather than another anti-religion perspective. That choice is not so implausible that you need to explain the coincidence away by saying that that's not his real reason and it must be status signalling instead.