To be clear, I'm not claiming that any particular implementation of PoS is vulnerable to this exact attack. It's an illustrative example of one class of attack that is a danger on PoS chains but not PoW chains, and might help people intuit why PoS implementations are more complex.
Coming back down to earth, this is why ETH requires checkpoints[1], but PoW chains do not[2].
ethereum PoS finality is part of the mechanical consensus protocol and established every epoch or two automatically, vs Bitcoin “checkpoints” that were hardcoded into clients. not really comparable