Gruber mentioned on The Talk Show with Joanna Stern that iFixit or someone pulled the Series 5 apart and it’s the same as the Series 4 (I can’t remember if he said it was exactly the same or the same battery… I assume there’s at least some processor difference).
Seems like the Series 5 is likely to be like the first iPad with Retina display (iPad 3, I think?) where it was not quite powerful enough to pull off the Retina display, and then the next version was much better.
Of course Apple couldn’t come out and say that the Series 5 had worse battery life than Series 4, because that would have been the second part of every sentence about the always-on screen in every review. I’m guessing next year everyone will be saying “Ah, yes, now the Series 6 can do the always-on screen with decent battery life.”
But I’m sorry to say that I think the Series 5 is always going to have this problem, even after the “fiddle factor” dies down.