Ok, but lets be fair while speaking,
The promo is 40x wagering requirement, with %2 house edge this is 80%, so 80% of (20 x 0.015mBTC), so in the end of rolling for completing requirement you are with 20% of (20x0,015 = 0,3(which is still very far from the withdrawal limit)) so = 0,06mBTC or 6000Sat.. or more less
This is very different from a promo with no rollever ..
The truth is, the chance of making 40x wagering is even smaller than what you counted.
However, I still like that someone who doesn't deposit gets free spins.
Of course, for someone who makes deposits and is an active player, the terms of this promotion are actually very unattractive.