The thing that seem odd to me about the overtime is that it’s really not very much time to be developing a weaponized form of anthrax. One would think that a lot more experimentation would be required. Even if one knew the correct procedure in advance to convert the liquid to such a virulent dry form, it seems like some trial-and-error would be involved that would eat up more time.
It's not very much time to do much of anything. I think the FBI is just floating that idea since it might seem credible to the average person who hasn't done lab work.
Even assuming growth rates an order of magnitude faster than what happens in live victims, you'd still be talking about 8 hours of time with a bioreactor (not counting set up time). Add to that the 5 hours needed for conversion to spores (that's a biological constraint of anthrax, so there is no way to make that go faster that I know of), and some period of time for drying (let's assume some rapid drying system by blasting it into a tank of hot helium gas via a pressurized nozzle, which might theoretically allow consistent particulate size based on the pressure used and the nozzle geometry), and you're talking about 14 hours minimum.