This is likely a 2017 vs 2018 thing. Online copy of the 2018 owner's manual has this on p.237:
The rear view monitor assists the driver by displaying an image of the area behind the vehicle while reversing. The image is displayed in reverse on the screen. This reversed image is a similar image to the one on the inside rear view mirror.
Picture on the page seems to say video output is only at the left little bit of the rear view mirror.
For year 2017, "rear view monitor system" is on p.17 of the quick reference guide. The whole section has like 4 single sentence paragraphs, then it says "For more details, refer to the Owner’s Manual details." Except there is not a single mention of the feature in the owner's manual. It does take up the whole head unit screen though. I use this all the time, so trust me
