Pretty sure this is all MS's doing. MS will only support PR3 in Kaby Lake and Zen, which is needed to to stream their 4K DRM content. Additionally, MS has made it quite clear that they will not add support for either in any pre Windows 10 OS.
So that leaves support squarely locked to a Windows 10 PC running a Kaby Lake or Zen CPU.
No wrong doing by Netflix, just a MS ploy to move ppl to Win10 and Edge to knock out their competitors.