An Amazon Fire Kids tablet was allegedly used to stalk a security pro

There's experts, and then there's "experts". One will have the sort of innate distrust for everything not entirely under their control which you're alluding to, while the other is an "expert" due to having received memorisation-based certification and basically does nothing more than parrot industry propaganda---or as they like to call it "best practices". It shouldn't be a surprise that far more of the latter exist.

Would you communicate with your team via post? Isn’t that 100 times easier to spy on / MITM than the asymmetric encryption used to secure most internet communication?

You neglect to mention that you'd have to be alone in those woods, at which point physical threats become a more-pressing domain of concern.

People are a liability. No wife, no kids, no problem! You could be the world's foremost security expert; it's no protection against them or their friends bringing this crap into the network.

Yes, I thought that was a bizarre lacuna in the narrative. This guy has two Kids tablets and all of a sudden it's in the hands of an adversary. Well, of course if someone absconds with one of your personal devices and gets full access, you'll be pwned. They left out the most intriguing part of the story.