Candidates joke about these terms to describe the viva, but I think the joke masks real fears. They worry that examiners will come in and speak harshly, treat them or their thesis with a lack of respect. They worry that they will come in with an agenda, a pre-determined outcome based on “the right way” to do research.
I can’t say this never happens. I can say that I’ve not heard of many viva experiences that match this fear. I’ve spoken to a lot of people about their vivas, and it’s not come up much. Talk to people from your field about their viva experiences. You’ll find that there are ways that examiners generally behave. They’ve generally prepared well, read your thesis carefully and have fair questions in mind to drive a discussion.
Listen to stories and get it settled in your head: if your examiners disagree with an idea, a method, a conclusion, they will treat you with respect and they will be open to your explanations. They’re not interrogators or inquisitors.