I've had a couple of delayed message notifications on the watch that I'd already read on my phone hours earlier (or in one case, the day before), but I also had a message notification show up on my watch that never showed up on my phone. I can see the message on the watch and on my MacBook, but it never showed up on the phone. In addition, my July activity challenge stayed on the watch into August. After a few days, I rebooted my watch and it disappeared, but the August challenge does not show up on my watch at all.