As the site notes, a GP104-based GTX 1060 has been present in NVIDIA's drivers for months now but so far we have not seen any models based on this SKU.
It is believed that GP104 GTX 1060 variant was made specifically for the Chinese market, where GTX 1060 is the most popular choice for Internet Cafes.Interestingly, the timing for the GeForce GTX 1060 6GB GDDR5X launch seems to somewhat coincide with the rumored AMD Radeon RX 590.
The problem with GeForce GTX 1060 series is that there are far too many variants. It is hard to keep track of what model is being tested or preinstalled in OEM systems. So yet another model is not going to make this any simpler.