Windows Central leak was first, so they couldn't misunderstood what Phil has said in regards to Xbox SX power few days later. Windows Central simply wrote numbers they were told without any interpretation.
Phil has said Xbox SX will offer 8x the power of xbox one, and 2x times the power of xbox x. If you want to assume Phil was talking about performance in general (not just TFLOPS) then these numbers dont add up.
Here I have explained why.
Is there a reason MS refuses to use the word Navi and says RDNA instead? It's technically more accurate I guess? RNDA is the architecture, Navi is assigned per-card codenames within this generation, and it's not any readymade chip. https://en.wikipedia.org/wiki/Radeon_RX_5000_series#Cards
www.neogaf.com
Therefore it's obvious Phil was thinking about TFLOPS numbers alone like he always did. 12TF is exactly over 8x times more poweful than 1.4TF, and two times more powerful compared to xbox x 6TF power.
If you remember Xbox x was also marketed as 4x more powerful console, yet it's more like 5x faster in real games. I'm telling you man, MS is aiming at 12TF (Navi RDNA+) and currently there's simply nothing that suggest otherwise.