Say mr X was seen at the crime scene at 10 am, he also knew the victim and lots of people have seen them fight a week ago, the victim had just came out of the bank with 20k$ in cash in a bag, mr X who's broke have been seen driving a car a month after the crime worth 18k$.
There is no evidence mr X killed the victim, but he probably did it.
Your argument removes probability, we have many coincidences linked to the lab leak theory, we don't have a 100% evidence that supports it, so we can assume it probably leaked from the lab, maybe it didn't, and since we can't quantify it with precision and a certain negligible error margin, we can use a language where probably happened means >50% and maybe happened means <50%.
A woman can safely assume her husband is cheating if she catches him flirting with girls online, find a different long hair on his coat everytime he travels for work, etc.