What would be the legality of stating " My password is not XYZ", when XYZ is the destruct password. Can you get the obstruction of justice charge if they try it and it destroys evidence?
Intent matters. If your intent was to trigger the destruction of data, you'd probably still be slapped with the obstruction of justice charges.
And judges aren't fond of people who are obviously trying to pull a fast one.
Here's an idea: write the self-destruct password on a post-it note and leave it on your monitor. It's the same sort of thing, but preemptively - it's not obstruction of justice if you're not under investigation when you do that.
How can the sentence "X is not Y" possibly specify the intent "I want you to try X anyway, to see what happens".
When you have prior knowledge about what X does (deletes evidence) and there's no reason to say "the password is not X" other than to trick someone into trying X as the password, that's how.
Because it's reasonable to assume that you know that a statement like that will arouse their curiosity. You're dealing with humans looking for some kind of actionable information, and with reason to believe that you may be trying to deceive them on some level or another.