The question is should we follow the security tips from the Ledger company that allowed such a data leak?
I wouldn't just blindly listen to security tips from literally anyone. But plausible deniability through a PIN/passphrase? It's not like it's a thing that only Ledger has and recommends.
In my opinion, plausible deniability in such a case won't help since attackers are usually well aware of any tricks that one may come up with a Ledger hardware wallet. You don't think they'll leave you alone after taking your $100, do you? Personally, I doubt it.
It is better to get rid of your Ledger altogether and try to persuade attackers you had sold all stupid bitcoins and stupid hardware wallets because it was dangerous to deal with those after a leak happened. Otherwise, once you show you still have it, you are most likely done.
The plausible deniability route is far more convincing that simply saying that you lost literally all your bitcoin to be honest. And it's more likely for them to not leave you alone if you left them with
$100nothing.
And sure, there's a decent chance that the thief might know about the temporary PIN trick, but it's at least worth trying to pull it off.