Get a small base die I don't think you are sizing your case body down enough and it's not sitting all the way into the chamber which is causing your bolt to not lock up.
Plenty of that data on Accurate Shooter you are correct that cleaning primer pockets when all you do is shoot steel isn't necessary but when you shoot for groups or f class that clean primer pocket might be the difference between winning and loosing
It won't damage the hydro press it will cause the gauge to read high it doesn't effect anything and really all you are looking for is a pressure spike or to stay under a certain number whether that number is 5 or 25.