Mine will turn my LG on, control the volume, do all of that, it just won't ever turn it off. The AppleTV will turn itself off, but the TV itself will revert back to its screen saver display complaining about No Input.
I've got a Apple TV -> Denon -> LG C3. CEC on the appleTV remote will turn all 3 on, and long pressing (power button on appletv remote) will turn all 3 off, not just screen saver with input.
My Samsung frame does that too, some TVs ignore the off CEC command. It might be a setting you can control on the tv. Last time I checked the frame did not have that option.
Once it's awake buttons presses on the LG remote are passed through to it but I have to keep the Apple remote around for that first step.