I do not find your explanation of the objective of PoS convincing. Maybe you are talking about their protocol that is true by construction?

Proof of Stake strategy is to make it where attacks on the blockchain are impossible in the economic sense. Proof of work strategy is making the attack infeasible by making the work required impossibly large.

Now is PoS possible? No idea. That possible fork attack seems like an impossible barrier to overcome. But we will see.