Besides the objection that government Bitcoin seizure is not impossible, consider your threat model. You arguably have less exposure to government seizure (again, questionable, to me), but you have far more exposure and less protection from more prosaic kinds of theft and fraud, which I think most of us are far more likely to encounter.

Bitcoins can and have been seized.

"They" need only seize you and beat you with a wrench to get your passphrase/convoluted security mechanism(s) protecting your private key(s).

Or just pass a law requiring you comply or else.

True but I can have a hidden bigger wallet

The size of your wallet doesn't matter when you're in prison or dead.