It's not deterministic, it's probabilistic. Bun does have memory bugs that would not be there if they'd written in safe Rust instead of Zig. You could imagine a scenario where ZigBun has zero memory issues, but it is not the most likely outcome, and is arguably an incredibly unlikely outcome given the entire history of software written in memory-unsafe languages.

I am less motte-and-bailey'ing, and you are more not subscribing to the principal of charity, choosing to interpret the original comment as its weakest possible version rather than the strongest.