It’s not just because of nonsense, it’s more that it doesn’t really matter what you do - the only thing stopping someone with physical access to your machine is their level of determination.

At some point, there’s no stopping the laws of physics. Your data is physically stored there. You can do a lot to make it really difficult to access it, but the best you can do is full disk encryption with a sufficiently strong key, and only store that key on external hardware that isn’t accessible to the attacker.

Even then, you better make sure that your encryption key wasn’t hanging around cached anywhere in memory before you shut down your computer.