Maybe they got anthrax from that source too, but didn't the Commerce Department approve sales of anthrax to them in the 1980's, and didn't that outfit then in Rockville and now in Virginia send anthrax to them?
However, the development of improved strains would accelerate if the strains came from Russia with built in advances.
Also the most effective way to create more virulent strains in a small amount of time is to use humans instead of green monkeys.
The soviets developed a strain of Marburg called Varient U named after Nikolai Ustinov, a Soviet scientist, who accidently injected himself with Marburg. After he crashed and died his autopsy showed that the Marburg had become more powerful and more stable.
So it's no stretch to assume that if the Iraqis have the means to test on people that they could develop bacteria and viruses that the Soviets only dreamed of.