This is indeed a very old problem and it strikes to me as odd that a complete menu item is present in Photo's (View>Sort) which is not user configurable.
My biggest problem is not the sorting in Photos app itself, but the subsequent order of the photo's on my AppleTV. It always starts with the oldest picture first. With the old AppleTV (version 3) however I had a work around. If I displayed the oldest photo full screen and then with the back arrow key on the remote I got the newest photo. If I then went one level up I was in the overview of the newest photos and could navigate without problems.
This week I got my new AppleTV (version 4) and the above mentioned work around does NOT work any more. Bummer...
It is virtually impossible to manually navigate my almost 28000 photos on screen to arrive at the newest photo. I
Does anyone know how to convince the Apple developers to make one very small change in a default ordering, which makes all customers happy? I can not imagine that there is a single customer who wants to start looking at his/her pictures from the oldest ones in their library first.
Regards,
Gerard