The nia does directly measure alpha and beta brain waves, however, brain waves are not precisely timed which makes them a bit difficult to use in games that require precision timing of events. Note that there is a difference between a device not being able to do something and a deliberate decision by the user to not use that particular aspect.

Also, I am somewhat surprised by the author's pushing his "muscle only" theory. Muscle signals are the easiest ones to control for beginners but there are other signals that are used by the nia as well, even for game control, especially the autonomous nervous system and the reflexes it triggers, not to mention the skin responses that are much more holistic than just "voluntary muscle movements" as the author wants to make us believe.

Also, just because another source (engadget) also quotes the information wrongly, that doesn't make it right.