"Battery life during our test period seemed to be pretty good and perhaps slightly better than many dual-core Android phone’s we’ve tested."
They weren't (except some games maybe). Most apps were written in Java and JITed.
Here's some more details: https://www.theregister.com/2014/05/02/arm_test_results_atta...
(note it's a 2-part, the "next page" link is small print )