I agree, you can’t require absolute certainty to act — it’s an impossible standard, but it does destroy the utilitarian calculation, both that and the fact that the results of the proposed action are never all in, the math and permutations are too vast.
Best we can do in legal settings is things like “reasonable person” standards and determination of intent. But the trolley problem and what it represents is the logic behind covid lockdowns, vaccine mandates and so many other horrors, i.e., it takes us ever farther away from a just society.