https://wccftech.com/new-apple-tv-4k-features-wi-fi-6-thread-and-hdmi-2-1/

Apple TV 4K with A12 Bionic has some notable changes under the hood, including Wi-Fi 6, HDMI 2.1 and Thread networking.

The HomePod mini features an interesting little tech called Thread which makes communicating between devices more efficient. This uses mesh technology and something which the new Apple TV 4K now fully supports. Given how the Apple TV functions as a hub for your HomeKit setup, therefore it makes sense that this tech is included here as well.