Native Client is an OPEN SOURCE technology which allows you to run NATIVE CODE inside your BROWSER (which no one said it is only Chrome) inside a sandbox which ensures you SECURITY by only allowing a restricted set of instructions to be run.
This is very very different from Flash.
Flash is closed source, you must pay a huge amount of money to access the development tools and all your code must be written in ActionScript.
Since Phoronix is, in my opinion, concerned about Open Source technologies, I think that Native Client is great enough to not be talked about.
There are plenty of games, which some are from major studios and publishers that are developed to be run in Native Client and could take advantage from many of the technologies that the Open Source community develops.
In Native Client you can take advantage from OpenGL ES 2.0 API and create console quality games.
I would suggest people who don't know what NaCl is capable of, to try these games:
Lara Croft and the Guardian of Light
These games, with great quality, were available to Linux users, months before Steam came to Linux.
There is nothing like that made in Flash.