... I am not really sure how to elaborate, to be honest. Rust prevents memory unsafety, but memory leaks are not memory un-safe. There are many kinds of bugs that Rust does not prevent. Leaks are one of them.

How can leaked memory, pragmatically, be considered safe? The language spec definition seems useless.

The only issue memory leaks can cause is being a DDoS vector. Memory unsafety can cause a host of other issues, and much more serious ones.

It is also very difficult to come up with a definition of "memory leak" that doesn't include programmer intention, and so it's not clear that you can come up with static analysis to preclude it.

Agreed there is not much you can do about a programmer using memory in an unsafe way...so what is the point?

You can, in general. Just not for memory leaks.

The point is defense in depth.