I also experience this issue last beta and watchos7 both drain my watch series 4 in about 6 hours when it used to last for min of 12. Called Apple care abd they think I need to replace the battery but it’s out of warranty... I kindly said that I don’t believe it’s the battery and to please find out what is causing this issue. I have restarted and link my watch 2 times today I will do one more test tomorrow. The biggest issue if this doesn’t get fix soon I don’t think this is the right company for me. I asked if I can go back to watchOS 6 but they said I can’t go back once watchOS 7 has been installed..... I am all in for improving software but if I’m getting only half of battery time in watch it’s not worth it.