Plus the fact that if this was a bioweapon, this would've been a HORRIBLE bioweapon as they killed and infected a large amount of their own people while doing this. Just saying.
War is based on deception. If they did have that information, they lose the advantage of leaving China in the dark as far as their knowledge of their complicity in creating and releasing this virus, and have less time to prepare if they make it public. Keeping the public in the dark regarding intelligence matters is the norm rather than the exception. No one said war is going to happen tomorrow.
This open discussion of the premise could very well be the administration slow walking the release of this information so as not to cause an over-reaction in the population, giving everyone time to absorb the possibility of such a reality piece by piece in a controlled way. You will notice this is also how the reality of the outbreak itself was handled as to not create mass panic over night, and create more disruptions and unrest.
The problem with your premise is that you assume that the CCP wouldn't murder millions of it's own people if it served the goals of the CCP. Additionally, bio-warfare is not just about maximum casualties. There are many types of weapons with varying levels of lethality for a reason, because each serve a specific purpose and use case in order to deliver a specific end result. The goal may not have been maximum casualty rate, but maximum infection rates and global spread. Ever hear of sappers? How about the Vietcong strategy of wounding rather than killing soldiers during the Vietnam war? The resources required to treat the ill and wounded are much greater than dealing with the dead, meaning less resources available to fight.
This could serve to disrupt the world economies, drawing out the amount of time other countries are dependent on China, and making rebuilding domestic infrastructure to decouple from China take much longer to acheive. That certainly has been one result of this outbreak. Additionally it gave the CCP a great excuse to effectively end all mass protests in Hong Kong, Taiwan, and elsewhere, along with an excuse to round up massive amounts of people for "quarantine", as well as a pretense for them disappearing off of the face of the Earth without a trace. There were many other results of this outbreak that the CCP benefited from as well. You go ahead and pretend this is outrageous, but the facts of the matter suggest significant motive for the CCP to take such actions. They certainly also had the means and opportunity to do so.