They're designed to work in all "modern" browsers, but have extra features on multitouch Windows 8 devices. Extra features ... and no ads. In addition, the Atari Arcade allows devs to create and publish their own Atari Arcade games through Atari's interface.
Pong seems like an odd way to emphasize the future-tech of your tablet, but hey, free Pong! Plus, a new development environment!