Yes, but the answer shows that you were aware of it before, which means you have already come in contact with the concept, leading to a higher probability for you to actually use it.
Then again, a tech savvy user that encrypts his drive and claims he/she haven't a slightest idea what the officer is talking about is probably in many cases way more suspicious. At least to an officer that is informed enough to bring that up.
Depends. How closely linked are the concepts of simple encryption and plausible deniability encryption? If you start researching the topic a bit you will stumble upon both, but if, say, a friend installed it?
I don't think that it does. I think the most it can be said to demonstrate is that you are aware of how the burden of proof is supposed to work in the United States.
In other words, it's his job to prove things, not yours.