Chance Miller reporting for 9to5mac:
The SDK for the device carries Game Controller support and the company mentioned it on stage at its unveil event. Apple also mentioned that games that worked only with third-party controllers were okay, meaning the games wouldn’t necessarily have to be compatible with the company’s bundled Siri Remote. Now, however, Apple says that games can not require the use of third-party controllers.
Apple are no doubt trying to avoid their customers experiencing the disappointment of buying a game only to discover that they don’t own the hardware to play it but it’s another ding against the Apple TV as a full fledged gaming.
The biggest challenge for developers will be balancing game play to ensure that the game is fun with both the limited inputs available on the Siriimote and the more advanced control schemes allowed for by a dedicated controller.
Source: Apple reverses stance, says that all Apple TV games must be compatible with Siri Remote