Risky for who? For the user or for the house?

The risk of 0 house edge for the site is the fact that they will not make a profit in the long run, is like trying to make money by flipping a coin, do a simulation with 10 million flips and you will see how it ends 50/50 or close to that number. Even if the event is random they follow a behavior.

But as Poker Player say, the risk is the variance, make 100 bets, with 50% chance of winning, if most of then lose then double the bet, and that way you can win in the long run against the house.