Yeah, part of it is to teach that they won’t get their way by annoying you into giving in. Helps in my case that I can be a stubborn fuck, too. It means I have to choose my battles because I don’t want to back myself into a situation where I make a choice, realize it’s not the best one, but feel like I have to stand my ground to combat whining. Luckily we’re past the point of tantrums and she’s old enough that I can explain my reasoning in cases where I say one thing at first but then later change my mind.
But there’s two other parts imo. One is teaching them the right way to express what they want (as well as when stating what they want might be rude or out of line, like if it’s in response to getting a gift that isn’t their top choice). And the other is being open and honest about the why. I only use “because I said so” or some equivalent to deal with the endless chain of "why?"s (though I’ve found deflecting it back at her is also effective, like “why do you think it is?”).
There’s a lot of space between “just let them carry on with whatever” and “beat them like I expected to be”. Not to mention, “getting my ass beat by my parents” might not mean literally getting beat, but can be a metaphor for any kind of discipline (though I can see how it can fall into the uncanny valley since there were and are parents that would literally beat asses).