Naming inconsistencies
vkEnumerateDeviceExtensionProperties is in this library as PhysicalDevice.EnumerateDeviceExtensionProperties, duplicating the term Device. However, vkEnumerateInstanceExtensionProperties is Instance.EnumerateExtensionProperties, the second Instance has been dropped. Same for Enumerate(Thing)LayerProperties.
The distinction here comes from Physical Device =/= Device - the Instance enumerate method is used for getting Instance extensions to create Instance objects, all sat within the same type. The Physical Device enumerate is used to get (logical) Device extensions to create (logical) Device objects, that are a different type than that which contains the enumerate/create methods.