You don’t want movies going from apple tv at 120 hz: it is a tremendous bandwidth at 4:4:4 color and can introduce banding and other color issues. Because even if apple tv manages to output that with 100% quality, tv may not be able to be fast enough to “chew” through that. At this rate priority is to show “something” fast enough.

ie outputting 24/25/30 is completely fine: tv will use corresponding multiples of frames by itself (120 for 24, 50 and 60 for 25/30, etc.)