I thought it was, but I had HDR OFF on the TV last night - Game Mode was enabled - and it still happened. I saw Slab's note and looks like that could be the root cause and not the TV setting.
Edit: I'm really clueless when it comes to this stuff. The beauty of 1080p was it was still plug in and play. The 4K looks amazing, but man, so many different options you have to account for now, so I feel like I'm flying blind at the moment.