I assumed that when you renounce your citizenship, there is no judge involved, it is automatic.
In that case, preventing coerced renunciations is easier than allowing anyone to renounce their citizenship but trying to allow the renunciation to be overturned and the citizenship reinstated afterward if it was based on coercion.
"It is automatic"? Depends on what you mean by "automatic".
In the hypothetical situation, a cop is holding me prisoner in my house until I say the magic words "I renounce my US citizenship", I'm pretty sure that nothing actually happens when I say those words. For example, my passport does not get revoked. (For that to happen when I say those words would require someone monitoring listening devices in my house, 24/7. We aren't there yet, fortunately.)
No, my passport would not be revoked until someone fills out and submits a form. (And some time after that, if I know bureaucracy.) Well, who fills out the form? The cop? Are the passport people going to accept the form from some random cop who recorded me saying the magic words?
Even if they accept the form from the cop... what am I going to be doing while the bureaucratic process does its thing? I'm going to be talking to my buddy the attorney, and my buddy the cop, and my buddy the retired cop, and my buddy the retired FBI agent. And somewhere along the way, someone is probably going to say something like: "Hey, he was trying to get you to renounce your citizenship - you should make sure that he didn't start something moving along those lines. And if he did, you should make it clear to them that it was under coercion, and therefore is not a valid request." And if I have to get a judge involved somewhere along the way, under the circumstances, I can probably do so.
So, it may be "automatic" - but it's not all that automatic.
Disclaimer: I don't work in citizenship law. I am just some rando on the internet. I say what I think, but I don't actually know how this would play out.
In that case, preventing coerced renunciations is easier than allowing anyone to renounce their citizenship but trying to allow the renunciation to be overturned and the citizenship reinstated afterward if it was based on coercion.