Peercoin has been around since 2012. So that's 2 years of history which shows this is nonsense. PPC peaked at 100,000,000 USD. That should be enough incentive to perform such an "attack". The answer is no. It does not even make sense.
Peercoin had centralised checkpointing, so not a good indicator of robustness.
I do not know about NXT, but PPC style PoS an be exploited.