Also, they do have an house edge, since they take BTC from your original bet. Send 0.01BTC? It's a 0.0098BTC bet to them, which adds up to a house edge. The house edge varies based on bet size, but there definitely is a house edge.
You are confusing House Edge with processing fee. As chain-bet.com is a blockchain based game, they deduct
BTC 0.0002 to cover their mining fee. This deduction is clearly stated when u generate an address as well as it is mentioned in their FAQ. Especially, now, as the Tx fee pressure is rising, I wonder, how they still cover with such a low fee! On the other hand, House Edge is simply the probabilistic edge house enjoys over gamblers, which has no distant relation with processing fee whatsoever.