I’m not using the public beta currently, and maybe you’ve already tried this, but in my recent experience I’ve found that uninstalling and reinstalling the Wyze app has restored the selected “App provided sound” for me. I think other Forum users have reported similar experience in the past, but it’s something I haven’t actually tried until recently. I was un/re-installing for a different reason but noticed the restored “Wyze Sound 2” as a happy consequence.
I don’t think removing and installing the app should be necessary just to get that one thing to work, so I agree that it’s still a bug. Notification sound selection should survive an app update.