The earth’s surface reflects almost 3 times as much sunlight as the moon does, making the moon look dark by comparison. But we never see a direct comparison between the earth and moon, except from space.
Per unit of area, that is approx. true.
But I suspect that the luminosities of the Earth and Moon in this image were, in any event, corrected. I namely highly doubt that the part of the Moon visible in this image was in sunlight at that time.
Regards,