It throws me back to regular watch screen everytime from the summary and it certainly makes no sense to me. I wish Apple allowed an override there. Anyway, just realized that I can also use the side button and swap back to WOD.Unfortunately the app can't control what watchOS displays when the arm is lowered and raised. When a workout is active watchOS is more likely to keep the app on the screen, but when the summary screen is shown then the workout has finished and the app has less priority. Usually watchOS will maintain the app on the screen but other things are more likely to over-ride it.
In terms of the brightness values I don't tend to show percentages in the settings screens on the iPhone app. However the sliders in the watch app settings have 10 discrete bars so it is much easier to exactly control the values exactly.
Ok, the 10 bars on the slider is good, I'd actually prefer if that would be the case in the phone app also.