The author wasn't ignorant: "I’m extremely knowledgeable of both Buddhist and secular frameworks of meditation, have read countless books on the subject."
This is not about ignorance, and framing it as such is directly supporting the thesis of the original article.
Regarding this particular slice of turkey on the table, since you insist: "[T]his is a misunderstanding that the Buddha himself addressed in the teachings."
The teachings? The teachings a person would likely be exposed to and eventually come up understand, if they've read countless books on the non-secular/Buddhist practice of meditation?
Regardless, if failing to "correctly" understand a bit of squishy woo-woo in Buddhist religion is the difference between safe meditation practice and psychosis/nervous breakdown, then that's all the more alarming.
This is, however, a moot point. The article is important and a warning to a lot of people. The current state we live creates such a tense situation for most people that these hardcore retreat-size meditation doses can literally act like shocks to both the trained and the untrained.