I've written many production Rust services and programs over the years, both sync and async, and in my experience—by far the most common use of mutexes is to temporarily violate invariants that are otherwise upheld while the mutex is unlocked (which I think is what you mean by "atomic"). In some cases invariants can be restored, but in many cases they simply cannot.

Panicking while in the middle of a non-mutex-related &mut T is theoretically bad as well, but in my experience, &mut T temporary invariant violations don't happen nearly as often as corruption of mutex-guarded data.