I'm from an ex-USSR country. You can't stop an authoritarian government with physical cash in your mattress.
Yes and no. I'm in Canada, so maybe the protests in Ottawa, which were mentioned above, are a good example to use.
It actually is much simpler for the Canadian federal government to just lock your bank account, than it is to raid a person's home and confiscate their cash. Entry to a person's home, or detaining them, invokes the entire set of constitutional protections against unlawful search and seizure and arrest. (And for complex, mostly stupid IMO reasons, your bank account does not.)
We do still have due process, judicial review, etc. If you were targeted during the protests without reason, and got a lawyer, you'd probably ultimately get the controls on your bank account lifted. But... you'd need to speak to a lawyer. And that requires some travel or an active phone plan. And that's where cash might actually help a lot.
There's also the question of scale. It costs a lot more, takes a lot more effort, to physically search for cash than to simply flip a bit in a database. Bank freezing can be done and applied at scale automatically, in a way that physical detention cannot. I do agree it is basically tending in an authoritarian direction. I'm worried about it and I'm not sure how we can and should fix it.
Nobody can confiscate what they dont know you have. You are making a case not to put all your eggs in your home.