If the agents are considered free in their betting behaviour within the confines of the decision theoretical proofs of the born rule in everettianism; would this not be also analyzed (under their interpretation of decision theory) as the agent having made both bets
so that (1) the world branches according to a bet A world and a bet ~A world and another branching into a A world, and ~A world
(2) should these be considered entangled; or two distinct branching; and if entangled couldnt they simplify their derivation by saying that the world either in on of two ways; (A bet A &, ~A, bet ~A), or [(A bet~A & (~A bet A)); or perhaps both but it already settled that by a previous branching which of the two the agent is in, so that know now that had they bet the opposite way, they would have had the experience of being in the opposite outcome branch, and would achieved necessarily the same result (if they bet A and win, had they bet ~A they would have won) or the other way around.
Of course the argument would have to be rather 'if they founding themselves betting A, rather then betting A; but for all extents and purpose it would appear the same to the agent)- there are no bets which take place, that is prior to the branching but rather the bets and position of the bet occur in the same branching transaction, after branching and as result of the same same branching that results in up or down
(3) if the betting occurs before the branching into spin up and down however, and it branches along both bet options before hand; then its a bit more difficult to make the relevant counterfactual claims; as there are four branches, and the other two corresponding to the other possible bet (one where you win, spin up) and one where you lose spin down) are already distinct and have already branched off; and if you bet both ways or the world branches in either cases, it makes it more difficult to compare them with each other; and one could consider both spin up branches, or the spin up branch bet up as identical in some sense as the spin down branch spin down as they both exist as distinct entities (unless there is some self-worlds transporting bets where these world are correlated).
Either way there will still be four branches, and the state of the entire multiverse branch system will be identical
(3) are the agents already in one of the branching worlds at the moment of betting; I mean if the state is in superposition, would the branching have already occurred and they would already be in one of the worlds; or is the basis or supersposition conditional on betting or some that basis spin x where up and down are equiprobable, being such that it will be selected, but it has not been selected yet; so they have no branched.