The parents for whom crossing a line resulted in verbal/physical abuse but were otherwise fine tend to have good relationships with their kids. While the punishment is much more severe than it would be in other families, there's a clear logical structure that a child can understand. When I was younger I would say stuff like "My dad hit us sometimes when we were being dumb, but otherwise he was great". However, I've long learned that people that grew up in the middle/upper class don't want to hear statements like that and get extremely uncomfortable, so I now leave it at "my childhood was good".
On the other hand, the people I knew growing up that had a father that was arbitrary with their anger tend to have non-existing/bad relationships with their fathers. I'd see situations where the father would tell their son to do X, son would respond that they've finished X already, father would lose their temper and scream at them to do X again, which made no sense. When you do that, you're not teaching a lesson or imposing any structure, you're just teaching your son that you're an asshole. Unsurprisingly, these children grow up with extreme resentment towards their fathers that has lasted into adulthood.