If you use upper-lower then you will forego combinations of bets that are sure gains. Dutch Book is inescapable, and only your presumption that the environment will contain agents who try to offer you losing bet combinations but no agents who are nice enough to take them, would lead you think that upper-lower "solves" the problem. No real agent can afford the computing power to be an ideal Bayesian, but the laws are ineluctable: whoever is not Bayesian - regardless of the reasons, regardless of whether it is unavoidable - is losing something.