Like yourself I am very positive about bitcoin moving forward, especially with all the issue going on in the world and during this crazy time in our lives. Now I can't agree that it's a "guarantee", as guaranteeing anything is a fools game. There are certainly never any guarantees in the financial world, especially for a digital currency.
"It is often said that Bitcoin is a hedge against uncertainty. And that's it". I am not sure what you mean about this exactly. Do you mean bitcoin is used as a hedge in a good way or people say it's the only positive factor of bitcoin?
In my own opinion about what the OP said regarding guarantee, is after you have bought some Bitcoin, you will have a guarantee to keep it after how many years if you didn't sold it out. you still have it even after your death because no one could get it from you unless they stole some necessary things to access it. if not, then the guarantee is a fact after so many years has passed the bitcoin is still there on your wallet.