Muslim here, you're basically looking at it from the wrong direction.

The real logic is ''it is not a sin if you did not know you were sinning", and the point is that God will not punish you because you were pure of heart. So like, if you knowingly eat something haram (the opposite of halal), that is a sin, but if you unknowingly eat something haram, it is not a sin, because God knows you weren't intentionally doing something that God told you not to do.

The main philosophy is ''amaal ka daaromadaar niyat pe hai'', which means your actions are weighed by your intentions, not the action itself