Native Client only really gives support for browser-based games. This export option will let you ship standalone games for Linux, that run natively on the platform.
You are not wrong. We will not be shipping the Editor for Linux, only export options for players that will run on 32-bit (x86) and 64-bit (amd64) Linux. We are only going to offer official support for Ubuntu Linux with vendor-made graphics drivers, but we expect games exported from Unity will run on most modern Linux systems.