I've thought about that, but for starters they'll know how much you have bought, then it's just a matter of how evil and desperate they are. In Solzhenitsyn's book, Gulag Archipelago, they would interrogate supected "wealthy" people without knowing their actual net worth but they'd have their ways of getting lots of people to crack. From what I read, if the torture/fear is too much and you'd rather hand over your wealth, best to not give a large amount (relative to what they think you have) early on, otherwise they might think it was too easy and that you could be hiding more. 

But it's definitely nice to know that they can never steal your btc even if they kill you, a nice big old F U.