The best demonstration is in the first video posted, notice when Charbax looks at the monitor. There on the top right are the frequencies of the two cores, and you'll notice the both of them jumping around a lot, independent of the other. Using the cores "on-demand" only when needed ends up saving a lot of battery power, but doesn't give you any performance loss.
I wonder if the drop to 1.2 GHz also serves to keep heat under control. It might not just be battery savings, maybe the small case of a phone doesn't allow for proper cooling to hit 1.5 safely.
I'd love to see some confirmation that the asynchronous nature of this chipset is what's responsible for the seemingly lackluster benchmarking.