Hello, friend!
As mentioned in your post, NG-fast, as the most advanced technology for copper transmission, has many advantages. However, copper lines have inherent limitations: crosstalk. Optical fiber transmission is not affected by crosstalk. In addition, the rate of optical fiber transmission is better than that of copper line transmission. Therefore, NG-fast is not widely used at present, but the mainstream is optical transmission. Sorry, I didn't find more information about NG-fast.
Thanks!