I'd be a little more inclined to believe that the person who wrote the document was a real expert if there had been a known case of these guys actually producing a biological weapon. This sounds a whole lot more like people who have never built a biological weapon teaching other people who have never built a biologial weapon how to build a biological weapon.
It's been known for quite some time that al Qaida and company have conducted lethal experiments with biological agents, even if at times inadvertently. You are also far too dismissive of them. Many terrorists and terrorist leaders have been well educated people: engineers, doctors, lawyers, scientists, etc. You should also keep in mind that al Qaida has previously canceled attacks because they were uncertain that a particular attack would produce casualties of a large enough number to meet their approval and maintain their "brand" as highly dangerous.