I guess that's because he is already seriously overload. Suddenly lots of Pascal card flashing request. He don't even have time to reply the query. Don't think it's impossible to open up more product line for the public.
Also, by considering the cost of flashing and shipping. 1070 or above make more sense. If you flash a TitanX, the cost is relatively low (compared to the card's price). But if you flash a 1060, you can effectively double the card's price.
On a user point of view, if I pick 1060, most likely because of it performance to cost ratio. If I willing to pay double, most likely I will prefer a stronger card, rather than pay that amount to flash the card.