Sometimes intent and outcomes matter, but the aphorism is simply not a good guide to understanding reality. It should be discarded.
The classic example is a hospital for treating cancer patients. Suppose that one third of the patients are successfully treated, while the other two thirds die of their cancer. Is the purpose of the hospital to kill two thirds of the patients? Clearly not, but that is the outcome.
No, that is not what the hospital does, and thus based on this heuristic, it is not its purpose. What a system does is not the same as the context-free outcome. It is the outcome compared to the outcome that could be expected without the system. You have to define your priors.
However, if the expected 5 year mortality for the cancer was 50%, and with this treatment 2/3 died, then the rule would apply. A choice to continue using that treatment could be criticized as equivalent to a choice to kill 1/6 more patients. Because despite the intention, the known outcome was more patients dying.
Good! You are thinking! In principle something like this should be the right answer. (But we can simplify it by simply saying that we expect the hospital to improve outcomes, even though it cannot cure every patient.)
But no, the truth is that this hospital was built to provide jobs for civil servants <https://www.youtube.com/watch?v=x-5zEb1oS9A>. The purpose of a thing does not have to be related to the outcome.
The classic example is a hospital for treating cancer patients. Suppose that one third of the patients are successfully treated, while the other two thirds die of their cancer. Is the purpose of the hospital to kill two thirds of the patients? Clearly not, but that is the outcome.