Even the security from 720 confirmations is due to rolling checkpoints which is a centralized protection.  Without it, it would be worse.

This explanation also ignores what we are talking about when it comes to history attack.  If at block x the attacker has 51% of the active stake the attacker can then sell his stake and thus the attacker has no cost, he no longer has any coins but as of block x he did so he can reorg from that point.   The attack can be done with no cost or risk based on the fact that in the past the attacker did have sufficient resources to perform the attack.