You are missing the point, by quoting out-of-context from the section with this big header: We optimize papers for the referee, not for the (intended) audience.

The author's issue is not with defensive writing. It's with writing to defend against the wrong audience.

Perhaps you haven't been in academia, and haven't experienced it yourself, but the author's problem is very real. Your intended audience will understand a point, and want you to go further. But the referees are often not the intended audience.

Imagine trying to explain the value of a new type of N95 mask to an anti-masker. You'll be spending your time writing defensively to try to argue for the most basic aspects of wearing a mask, when you would really just like to go into details on what's cool about the new type of mask, for people who actually care about better masks.