I don't think it's all about blame, knowing it came from a lab would also pull into question the practice of engineering viruses and the safety and security standards required.
If it is possible that viruses of this type could be engineered, then lab safety needs to be upgraded anyway (or GoF research banned, or both) regardless of the origin of this specific virus.
It’s all about blame. Blame
is a useful geopolitical tool.
That said, the blame game would still be there, and people would pull that card...