Isn't that only an issue for a chain that's starting from PoS from the beginning? Ethereum already has a PoW chain that they plan to turn into PoS. If the ether

Isn't that only an issue for a chain that's starting from PoS from the beginning? Ethereum already has a PoW chain that they plan to turn into PoS. If the ethereum protocol agreement is to switch to PoS at block N, then I don't see how you can create a valid-looking N+1 block without yourself putting a large amount of real eth at stake.