Yes?It is not just that we don't know. It is that there is no answer to that question, for there are multiple ways to interpret what the word 'benefit' might mean. It is a vague word with no specific meaning. It is only after we assign a specific meaning to it, whatever it is, that we can use our knowledge to look for the best way to achieve it.
I fail to see a problem. But we might not find what the benefit is. If God tells you to wear green dresses and never blue dresses, he clearly knows why this is. To humans it would seem absurd. Yet if we believe God is not malevolent, as in the Classical Monotheistic paradigm I'm working under, then we assume God sees benefit in wearing green dresses as opposed to blue, or some disadvantage in blue dresses. The easiest way to achieve whatever benefit it is is to wear a green dress, even if we don't know the good of it.