Probably requires the newer generation accelerometer. There are also other issues like power consumption overnight. Older watches have smaller batteries and sl

Probably requires the newer generation accelerometer. There are also other issues like power consumption overnight. Older watches have smaller batteries and slow charging. People will update the software, use the new features, and complain that Apple software updates are killing the battery (waking up to low battery plus slow charing means not being able to charge up before leaving for work). This has the effect of Apple only backporting new features if they don't consume too much battery.