All four games make heavy use of Windows 10 eye-tracking APIs that were introduced into the OS as a part of Windows 10 version 1803, which in turn, built on the "Eye Control" accessibility feature that was introduced in version 1709.
The company sees it as a perfect win-win scenario. People with the aforementioned disabilities get four fun games they can play. The company gets the opportunity to study, assess, and improve the technologies to open the door to new eye tracking technologies in the future. It's also a good proof of concept that Microsoft hopes will drive developer interest in creating new games that make use of the APIs. In fact, the company is counting on it and has even created a Gaze Interaction Library on their site.
If you're interested in testing the technology out for yourself, the first thing you'll need is a compatible eye tracker. Once you've got one, you'll need to enable the "Eye Control" feature under the "Ease of Access" section of your system's settings. From there, it's a simple matter of downloading and installing the games you want to play and getting to it! Of course, while all four games were designed with eye tracking in mind, it's also possible to play them via mouse or touchscreen controls.
It's an exciting new technology being put to fun, playful use for testing. Kudos to Microsoft!