Not necessarily. These three models are the simplest ones - and our universe has a much different matter distribution than any of the three. It's still possibl

Not necessarily. These three models are the simplest ones - and our universe has a much different matter distribution than any of the three. It's still possible that adding more features to the solution, such as mass or angular momentum, changes the stability. It's also possible we do live in an inherently unstable universe, but even unstable things can have long periods of time elapse before breaking down. It's mostly an interesting mathematical curiousity.