Do music playlists do live updating on iOS 13
While I don't have a smart playlist with a limit of hours, I do have lots of smart playlists with various criteria. In my experience, all of my smart playlists update automatically on my iPhone and iPad.
Performing an action like playing a song which would add the song to the smart playlist makes the song appear in the smart playlist immediately for me as it would on macOS, even though the criteria can't be viewed or modified on iOS.