This is incorrect. The statistic of 5.8 liters per hour is actually liters per hour per square meter. A 10x10cm panel would produce 58ml per hour in full sun. If you instead put a solar panel with 20% efficiency and used the electricity for reverse osmosis you would produce about an order of magnitude more water per square meter. This may have lower capital or operational costs, though, and it is certainly more decentralized, so it could be useful in some situations.