The part that makes this is big leap is that they had to correctly ascertain that the right countries wouldn't take this seriously enough, quickly enough, for this to be effective. Essentially if this was targeted at the west, they had to gamble that the West would value commerce over life, and allow a LOT of people to die in that pursuit. If they quickly and effectively shutdown and attacked this, it wouldn't have been an effective weapon.
The second part is that to be able to call this a bio-weapon, you also have to accept as fact that COVID was a very deadly pandemic, and that taking precautions against it IS the right thing to do. Otherwise if it isn't worth being vaccinated, masked, and distanced against, it was a pretty crappy bio weapon.