Did Etherium actually switch to proof of stake? That's been talked up for years, but has been delayed several times. The original date was January 2020, but as of now, I can't find a firm date. One Etherium page intended to get people to lock up ETH to stake the system says "Withdrawals won't be live right away. You won't be able to withdraw your stake until future upgrades are deployed. Withdrawals should be available once mainnet has docked with the Beacon Chain system."

It's always a bad sign in the cryptocurrency world when withdrawals are delayed.

The paper is written as if the change to proof of stake has happened.