The post said "all the experts are saying may actually be true". The "may" (not "is"!) there is pretty key in making the meaning a lot closer to your (B) than anything like your (A)... Did that comment get edited after yours? Because it seems like you are arguing against a strawman, not what was actually said.

But that is not the difference here. The original post said "Something [meaning the lab leak theory] all the experts are saying may actually be true". This is somewhere in between your A and B and at least to me sounds closer to B than A, as "may actually be true" is more of an acknowledgment of possibility than an assertion of probability. It's definitely not a statement of certainty.

But the statement in question was not "all experts agree that covid comes from a wuhan lab", it is "all experts agree that covid could come from a wuhan lab". That's still unlikely to be 100% accurate, but your version A is a complete misrepresentation.