It's natural for busy people in chaotic environments to misspeak. Our brains are doing many things at once while also trying to convey an idea/thought verbally.
It's a side effect of stress/pressure/multi-tasking. It's not an indication of intelligence.
A smarter person, with a better command of the language, will be better able to negotiate those difficulties. So the ability to speak effectively under stress really is a sign of education and intelligence.
Nobody disagrees, the article is pretty clear that it's all good fun.