I'd say that at that point, it doesn't even matter that you're writing Rust code. Most of the slimming down comes from cutting out cruft that the linker puts in by default.
Well, it matters in that Rust lets you eliminate this in the first place. Not all languages let you do this kind of thing. If you want to write Ruby, you have a VM, even if your program is `a = 5`.
Of course, it's not usual Rust code, but no binary that small is usual code, even in C.
The point is to demonstrate that you can strip Rust down to as small as you want/need, not to suggest that every single Rust program is ultra-tiny.