UHD (4K) playback?

the infuse page lists “Silky-smooth playback of 4K (Ultra-HD) content” as a feature. Is this really possible with Apple TV 4?
If I start a 4k video my TV still shows the input signal as 1080p. Am I missing something?

Thanks in advance

I assume that this just means the 4K content can be played and it is smoothly down scaled to the 1080p resolution that is the maximum the ATV4 hardware is capable of.