That's the whole problem though. They aren't using it which means people with systems that have height channels are going to lose out because Sony decided to go with a proprietary format route.
I guess we're just looking at it differently. I think Sony's only goal is to simulate 3D audio effects using only 2 channels, whether that be headphones, TV speakers, soundbar, or home theater speakers. For all we know using your receiver's upmixer could be better than what Sony comes up with. As it is their Tempest Audio isn't necessarily better than Atmos for Headphones. It's just a different implementation.