The Vulkan bindings do not require natives to work. LWJGL calls the functions provided by the Vulkan loader/driver directly (via the org.lwjgl.system.JNI class, which lives in the core LWJGL library).
The native jars for macOS are there because macOS does not natively support Vulkan. They contain a build of MoltenVK, which is a Vulkan emulation layer over the Metal API.