Operationalizing the "benefit of humanity" is hard to measure for someone else.

Someone else might cheat–Goodhart's Law

But inside yourself it's clear.

You know if you're cheating or not.

Do your intentions align with your actions or not?

If you have to decide if someone else is doing it it is hard, just judged by their externally visible actions.

If it's just you then it's easy, trivial, the most natural thing in the world.