So one of my other co-workers who has been using iOS 13 Beta 5 with WatchOS 5.3 since last week, and who has been pretty upset that he's had to charge it halfway through the work day, and then again at some point overnight, due to the poor battery life, decided to install the latest WatchOS Beta. His battery life seems to be a little bit better (standby and usage times are about an hour or so apart, as he just installed the WatchOS beta a couple of hours ago). Now, however in the Health app, it's saying that "This Apple Watch is no longer paired with this iPhone" and he's not sure if it's even recording/logging any of his activity, etc.
I recall that I had this same issue when I was using WatchOS 6 Beta where it also showed that in the Health app (I think it was still however tracking activity, etc.).
I am debating installing the WatchOS Beta again, as I can't imagine there's more than 1 1/2 month +/- before both WatchOS 6 and iOS 13 will be released (how complete or stable it will be is another thing, and likely won't be "ready for prime time" until it hits 13.1 or so).
Anyhow, anyone who is running the iOS 5 Beta and WatchOS 6 Beta, can you check in the health app under devices and see if it shows your watch as "This Apple Watch is no longer paired with this iPhone".
Thanks.