The Wayland Dev's message was directed at the wayland-devel mailing list, anyone on there certainly is well aware of what Wayland is. It would be quite unfair to say that a simple release announcement, on a development mailing list, must include a description of what exactly the project is. It wouldn't really accomplish anything at all. Especially a project like Wayland, which is still quite a ways away from being all that relevant to people that aren't working on the Linux graphics stack (most of which are likely well aware of Wayland by this point).
LWN did, in their blurb, refer to Wayland as a 'display system', which should lead most people in the general direction of what Wayland is.