I'm using the Harmony "BT Apple TV" device with "Windows PC", and the rewind and fast forward button profiles (from the "Apple BT" device") act similar to that of a Tivo (or other cable) remote where each press of the button increase the speed of the rewind or fast forward. I have noticed that this functionality currently works in streaming apps like Disney+, but using the same Harmony setup in the Channels app functions like the normal Apple remote of skip back/forward a set amount of time like 15 seconds. Seeing that the AppleTV supports this stepped increase in rewind/fast forward speed, would love to see this support in Channels as it's slow and difficult currently, especially using a non-Apple remote with no ability for high speed scrubbing.
*** EDIT ***
Closed caption is now magically working, so please disregard
EDIT
Also, the "c" press on the simulated Windows keyboard does not turn on closed caption. Logitech actually adds a period, so "c." after all of their lower cap mappings, so maybe their issue, but the "m." mapping works as the Apple TV mute.