From my view it seems like for a website to have such feature you might given access to phrase or person keys~
If you bother to visit the website, you should be able to see that the site did not require such kinds of things. The information that I referred to on the MetaMask link above should also suffice to get a grasp of what this kind of platform can do.
The platform is also open-sourced, so you can run it locally and those who can inspect the code are able to do it. It is one of the listed smart contract revoking tools that listed by MetaMask: How to revoke smart contract allowances/token approvals.