All it really proves is that humans cannot comprehend distance as vast as this.
My understanding, and im sure its flawed, is that something like a Photon doesn't experience time. To it, it pops into and out of existance, one end at the surface of a star in a galaxy cluster 12.7 billion light years away, the other end at the Subaru telescope in this case. Just as suddenly as this happends, its gone again.
This is because its traveling at the speed of light. Time and space are linked. Beyond this my understanding breaks down, but I suspect it has something to do with moving through space at that speed, and our misunderstanding of what time really is. We experience time where there is a 'universal' time in our refrence, because really anything we need to reference is already here, moving with us at the same speed around the sun. There is no 12.7 billion years ago to this galaxy, per our reference, because nothing that is happening 'now' as you and I understand it can possibly affect us here, without violating the speed of light. We're not looking at a galaxy we're literally looking back in time at a galaxy. If this galaxy exploded ripping a hole in the fabric of space-time and ended the entire universe right now, we'd not be aware of it for another 12.7 billion years. Per our reference, nothing has happened, or will happen, for that span of time. So in effect, for us, what we're seeing is what IS happening.
Now please correct my misunderstanding, those of you lurking out there who do know better, because i'd love to understand all this!