They are saying that financially, P/E on a stock (really, E/P) you buy is the same as APY on a deposit/loan, since both are the return on invested capital, and you can cash out your principal later.
Oh course their are subtle details that cause volatility and risk of collpase based on how the company/bank/borrower uses the money you put in.
When you stake, you are using your own money to guarantee that transactions on a network will process successfully. If something happens and they don't, you lose that bag.
Staking is just a very stupid loan that you give out without having any real insight into the people who borrowed from you.