Rewards from staking after The Merge

Bankless article https://newsletter.banklesshq.com/p/dont-sleep-on-the-merge-lite?s=w

claims that:

"Once this 10.5m ETH merges with the PoW Ethereum chain, that yield goes from 4.8% to ~10-15%. That’s a 2-3x increase in returns:

• A 2-3x increase in the incentive to hold ETH.
• A 2-3x increase in the incentive to stake ETH."

How is that conclusion reached? How it can be 10 to 15%? Will The Merge upgrade double/triple the returns from staking by itself that I do not know of? Is it reffering to tips that will be given to validators? What am I missing here?