yes, sure but still according the calculations and imperfection of the person, there is a 0.87% edge so, when they are putting on the top it means they are taking let's say 1.87% edge.
No, 0% house edge = 0% house edge.
Most bitcoin (dice) games have a 1% house edge. Some even 0.3-0.5%. That is very low already. There is nothing "on top". The casino still has a risk to lose (a lot) of money short-term as variance can be bad (and good for player obviously.) So I think it's fair.
The only way to reasonable have 0% house edge games is if it's player versus player. But generally the entertainment/usability for the player is less that way, so these sites generally don't even get popular despite the 0% edge.
edit: There are some games like blackjack or video poker where the play/skill of the player changes the expected profit. I guess you were talking about that. In that case 0% HE is somewhat possible. Most gambling games (dice, roulette, slots, etc) don't involve "skill" though.