I'm not aware of any definition of metastability that would be a desirable property of a system. Vaguely speaking, in my understanding metastability in physics, chemistry and electronics refers to a state that has not yet fully settled and the final state is therefore undeterminable / random.

Could you elaborate your understanding of the term? I can see it related to concepts like eventual consistency, just unclear of how it would be considered a positive characteristic. I'd have thought that a deterministic outcome would be important in a database system?