I don't understand how the situations you are describing are different between PoW and PoS.
In either case, after a fork, sympathizers of chain A or chain B will start mining/staking on the chain they like.
In either case, members of the public who just want the chain with the most security can pick the one with the most energy burned or most coin-days staked (that's the "hash rate" equivalent/external input with which to base your decision on).
What is the difference? How is human intervention inherently required in the PoS case any more or less than it's required in the PoW case?
If “coin-days staked” is massively higher on one side of a PoS chain fork, that doesn’t impact the other side’s security in the way PoW hashrate imbalances would.
To use a real world example, Bitcoin PoW mining consumes in excess of 100 Terawatt hours of electricity per year. If Bitcoin were to undergo a repeat of 2016 today, and the Bcash blockchain were to be serviced by miners consuming less than 10% of the energy spend of the incumbent (Bitcoin), Bcash could be easily 51% attacked.
But in the PoS corollary to Bitcoin v Bcash, coin-days staked would have no bearing on Bcash’s ability to continue making forward progress. Just so long as it remained difficult to either disrupt 1/3 of Bcash validators or acquire 51% of it, Bcash would continue functioning perfectly well (see: Jude C. Nelson [1]). At that point the rightful heir to the Bitcoin title would have to be determined socially. It could not be determined without top-down human intervention.
> But in the PoS corollary to Bitcoin v Bcash, coin-days staked would have no bearing on Bcash’s ability to continue making forward progress.
How wouldn't it? The ongoing coin-days staked in that fork specifically is what allows it to continue making forward progress. Just like how in a PoW fork, the ongoing consumption of energy in that specific fork is what determines the security of that fork.
The argument you link in that other thread is interesting but it doesn't appear to be exactly what you are talking about. They seem to be describing an attack where nodes are taken offline by the attacker.
> The ongoing coin-days staked in that fork specifically is what allows it to continue making forward progress.
Coin-days staked has no bearing on a pure PoS chain’s risk of being 51% attacked, nor does it have any bearing on the risk 1/3 or more of its validators get disrupted. Not so with PoW hashrate: enormous hashrate imbalances between forked PoW chains directly translate into decreased data immutability per the risk of deep chain reorgs.
Those risks are simply not present in the PoS corollary.
In either case, after a fork, sympathizers of chain A or chain B will start mining/staking on the chain they like.
In either case, members of the public who just want the chain with the most security can pick the one with the most energy burned or most coin-days staked (that's the "hash rate" equivalent/external input with which to base your decision on).
What is the difference? How is human intervention inherently required in the PoS case any more or less than it's required in the PoW case?