The leaked CPU-z benchmark (that you of course quoted) was multi-thread and in that regard it actually outdoes it by another 10% and if you can't understand (or rather pretend you don't because it doesn't suit your red agenda) why an aggregate of all tests can never be so high (not even 5950x is 50% ahead of 5600x), we can have no further discussion.
And oh, Vega was crap that couldn't even compete against 1080, never mind the 1080Ti, both of which came out before (way before in the case of the former). You could tune the 56 to about 1070 power and performance, but that one was much cheaper, so what was the point in that? Either way, the market had it's say and the fact that they never achieved any penetration is saying enough.