For those affected, I've very pleased to see that the latest TVOS beta supports frame rate matching on the older HD AppleTV 4thGen
https://9to5mac.com/2018/01/24/tvos-11-3-beta-1/
"Apple TV (fourth gen) now supports frame rate matching, previously required Apple TV 4K"
https://9to5mac.com/2018/01/24/tvos-11-3-beta-1/
"Apple TV (fourth gen) now supports frame rate matching, previously required Apple TV 4K"
