I think the implication was that memory encryption could mean that a rowhammer-induced bitflip would be amplified into scrambling the entire word of memory, which is more likely to have catastrophic effects than a single bit flip. That would be true for any reasonable definition of "stable" that admits any susceptibility to rowhammer.
But that’s a good thing. Sane state would be synced to disk and any successful bitflip will halt a system telling you that something bad is going on. It would be “catastrophic” for runtime but not for the data