I don't think you are correct on this one, iPhone 3 was released 2008 then 4 had completely different hardware design in 2010 then 5 came in like you said iterated on and polished with again noticeable design changes and then 6 had completely new design in 2014 so in a span of 6 years and 4 generations of product you had a new design for each generation, so no it is not odd for Apple to do good hardware design they just stoped because it is easier I assume changing one hardware design element will disrupt the whole supply chain so yes they became very conservative with their hardware designs.

My Huawei Watch GT 2 is a few years old and the battery life is (and always has been) better than my wife's (new last year?) Apple Watch SE (GPS) 2nd Generation. They do exactly the same things.

I simply don't understand why the Apple Watch is so pap. My watch lasts all week if I go on holiday, and my wife's is dead won't last much longer than a day.