More like it's a bad sign for other 2015 flagships.
Even the S6, with all the cutting-edge and energy efficient technology, only managed to squeeze out 5 hour SoT with 24 hour usage from the 14nm power-hungry ARMv8 cores. What makes us think that other flagships using the 20nm reference ARMv8 cores with even worse tech will do any better?
I said that the M9 will have worse battery life than the S6, and I was correct. I'll also predict that the Z4, G4, and other 2015 flagships will have worse battery life than the S6.