Plus "none of the above" is always an option. You could have 3 theories that all have very little supporting evidence - one of those theories could be the most likely of all the actual theories, but "none of the above" could be even more likely if the best theory is still weak.
It sounds like it's just semantics but there's a world of difference between saying a theory is very likely correct and saying that it's the most likely of competing theories.
- No idea for either solution and we'll never know - 70% chance
- Lab leak - 20% chance
- Occurred in nature - 10% chance
In that case, you could say that the most likely answer is "lab leak" if you must have an answer, but it's very "low confidence." I don't know what the actual odds are, it's just made up for demonstration.
Its fairly standard SOP. If you don't know what it means that video explains it fairly well.
What those phrases mean is that the lab leak is simply the least crappy theory.