Ok, lets consider for a second our beloved Phil (never lying, misleading, and one and only) was talking about GCN TFLOPS.
In order to match 8x xbox one performance, you would need 11TF GCN Vega architecture, and probably even less like 10TF because Vega was already more efficient than GCN found in xbox one s. So in order to match 10-11TF Vega, you would need just 8TF Navi, and maybe even 7TF (and especially if it will be improved or customized RDNA 1.5-2). The thing is, 7-8TF Navi would be not enough to match 2x Xbox X performance. Therefore there's simply no way Phil is talking here about GCN TFLOPS.
If however we consider Phil is talking about Navi TFLOPS, then everything adds up:
Xbox one s is 1.4TF, multiply it by x8 times and you get 11.2TF, so 12TF would be exactly a little bit over 8x xbox one s TF power (not performance), and exaxtly 2x times xbox x power. With leaks confirmation on top of that (windows central is very reliable site, and even Klee has confirmed it) there's no longer a valid reason to consider GCN TFLOPS, when everything points to Navi TFLOPS.
Just look at xbox SX case... it's really ugly, but at the same time it also suggest powerful and hot GPU inside. I'm 99% certain MS is aiming at 12TF Navi.