1293W is the power drawn at 12V side. +10% is added, when you calculate power drawn at wall, using Bitmain APW3-12-1600-B2 (effiency 93%) .
It's not that bad way to describe power usage.
It is 100 percent accurate you are right on that. They mention a range and it hit's in that range. It has taken a lot of flak though.
If they would have shown specs with 1400 and a much smaller percent, it would have made people happier. In my batch 8 thread this was a hot topic at first as they did lose efficiency from earlier S7's in first bit of batch 8's shipping.