I disagree with you on that 'they have every right to do so'

If a bet is in a status where it can be rejected by the oddsmaker, then it is only fair that the person placing the bet has the option to cancel it as well, especially over a long period of time.

That is not the case with sportsbet.io. Once I hit submit, I am at their mercy for the next few minutes and have no option to cancel, while they can hold and hold and hold and hold and decide what to do.