Cold storage does not mean irretrievable or inaccessible. It just means securely stored on a device that isn’t connected to the Internet.

Coins can be taken out of cold storage at a moment’s notice. Indeed, that’s what happens whenever anyone storing their coins using this technique decides to move or spend them.

You appear to be under the impression that some large portion of the supply is “frozen,” but that’s not what is meant by the expression “cold storage”. It simply means the information needed to spend them is being held in a manner that protects that information from Internet hacking.