For what it's worth, I have the Facetime icon available on my 2021 ATV 4K now. So the latest and greatest isn't required for this particular feature, at least. A test Facetime call I made was incredibly buggy with choppy audio, but the video quality was outstanding on my 4K TV. I was using a new iPad Mini and it only let me use the front facing camera, so my video was terrible, but the person that I called looked great.