I get what you're saying, and I agree this sounds like operator negligence to me. But the article does say that investigators had to get another aircraft set u

I get what you're saying, and I agree this sounds like operator negligence to me. But the article does say that investigators had to get another aircraft set up with the same modifications and fly it around with bits of wool all over it in order to understand the stall characteristics. So I assume this plane setup isn't so widespread that its stall behaviour is common knowledge.