I just purchased the Apple 4K yesterday and while it's kicks into Dolby Vision just fine and I'm using 11.2 firmware, I have matching range and frame rate set to on, SDR (playstation vue app) is being shown as if it were in Dolby Vision, activating Cinema User mode. There is nothing in 4K coming from that app. A B&W movie with Bing Crosby and Fred Astaire was showing as being in Dolby Vision.There are two FW/software updates you need to run, and then you need to change to a different picture mode when watching DV content . . . .
1) Update your C7 to FW Rev. 4.70.30 - The auto update function may say there is nothing to update. Get the direct download. Download both the file and the installation instructions: http://www.lg.com/us/support-product/lg-OLED65C7P
2) Update your AppleTV 4K to tvOS 11.2 - This is the new "must have" major update with frame rate and dynamic range matching integrated into the video settings options.
3) When watching DV content choose the "Cinema" picture mode, and NOT "Cinema (Home)". If things look a little dim to you, increase the OLED Light a bit to 60-80. I run it around 65. 80 would be the max.
Things should look much better afterwards.
In a nutshell, with Dolby Vision active in my Apple TV, everything is being sent to the TV as Dolby Vision.