How would this work from a practicality purpose?

If I buy an NFT all I am really getting is a hyperlink to an image (or otherwise) hosted on the web somewhere. That link goes dark and my NFT is even more worthless than before.

From a documentation perspective, does the SBT actually hold the data or just link to it? If a gaming item is contained in an uneditable SBT but later discovered to have a bug, what then?