they're talking about high schools, not 6th grade.
The guy teaching programming at my old high school didn't know jack shit. Well okay he knew enough to explain the elementary concepts in the book but he was far, far far from an expert in CS. Usually the job falls on math teachers or science teachers because generally speaking the number of CS grads from a reputable school (not ITT tech) available to teach high school is zero.
Having math teachers teach programming might be OK for getting the kids' feet wet and letting them know that such as thing exists, it might be okay for the average student, but even a slightly above average student such as myself back in the day (yes i was only slightly above average) will be bored to tears. But I suppose in today's world where everyone gets an equal education and no student is allowed to be left behind or get ahead, this may be desirable.
I think the somewhat bright kids are done the most disservice. The super bright Zuckerbergs of the world will just figure stuff out by themselves and do any kind of coding they want. The average and below will be happy to just follow along and get a passing grade. It's the somewhat bright kids who could benefit most from an expert teacher explaining advanced concepts and answering questions and pushing them to higher standards that they wouldn't have had otherwise.