Actually, I would expect a science writer, who has studied physiology and yoga and deigns to write about it would understand that rotation and flexion are two quite distinct spinal movements and that the postures that he is talking about indicate a flexed cervical spine, but no rotation (to be fair, it is absolutely a way for a student to hurt themselves if they choose to 'look around' and rotate their neck in Shoulderstand - that's a truism, but not what he is discussing).
It's quite simple - turn your head over your right shoulder, you've quite possibly been able to safely rotate your head up to 90 degrees... drop your chin to your chest, you've quite possibly been able to flex your neck approaching 90 degrees.
Of course, in an inversion, with the added gravity, for 90% of casual practitioners, Shoulderstand is contraindicated. But, somehow a man who is trying to inform us all about the dangers of a yoga teacher who has such limited training in anatomy - one of many commentators biggest concerns is the 'limited amount of anatomy' that is studied, and to be fair, 20 hours is not a lot to learn if you start from scratch and intend to guide physical movement. However, for a science writer who seeks to be published and comment from his authority, he obviously is not coming from a place of information, experience, or investigation (former hallmarks of journalism, abandoned almost completely in modern media).
Very troubling - and, in my estimation, low-leverage fear-mongering, limbic-system engaging panic is not informative or elevating. This conversation can be rational and based in truth, but that was not the impression that is given... seems like he wants to help sell a book and now is enjoying his time in the light.
No dispute that there are many, many, unsophisticated or less than talented teachers out there. Apparently, the same can be said about journalists.
Here's my advice - grill your teacher, ask them their background, their practice, their training, how long since their last training, what is their intention in teaching, have they studied anatomy further than the minimum expectation?? If you are pleasant, and inquisitive and get answers and have a dialog, that's in everyone's benefit. If the teacher is shocked, not responsive or defensive, you have all the answers you'll ever need there!
No effort on this path is wasted - effort is not pain, effort is not excessiveness - effort is presence and intention.
GIve thanks and praise - multitudes are healed and blessed; few are harmed, and those who pay attention will know the difference.