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. Lots of thought experiments being put on paper as instructions as if they were tried and true methods.
I can do a write up for how to build a nuclear bomb for my terrorist brothers based on my rudimentary undergraduate physics education, but there's no way in hell those instructions would actually produce anything useful.
The Bubonic Plague strikes me as a bit of a red flag. I don't know much about biological warfare but the Bubonic Plague strikes me as something you talk about if you don't know anything about biological warfare and just want something that sounds bad and has historical connotations.
Even if they had a good disease I still think it's a terrible plan.
If they target a western state the health care system will make it mostly useless. If they target a middle eastern state they're at war with it will be worse than useless, the target state will have better health care than the neighbouring ISIS territory, the plague could easily boomerang and devastate the ISIS controlled areas far worse than the target state.