HDR+ minimum bandwidth is 25Mbps but as someone who does stream 4K from their home media server you need a minimum of a 1GB connection from your media server to your AppleTV. They can advertise this feature all they want it will not work with any sort of quality until we all can stream at 1GB speeds from that provider. Their bandwidth requirements would be astronomical. So we are effecively paying for quality a little north of 1080 but not much. Definitely not even Blu-Ray quality. I assure you.
I don't know about HDR+ but Apple TV has no problem playing Dolby vision at 4k from Netflix or Apple TV plus with ~ 100Mbps