> 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.
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.