Bias denied.

First I make no claims about the outcome of the negotiation so there is no way privileging any dependence over any other could bias my estimation thereof.

Second, I didn't make any claim about any actual dependence, merely about communication, and it would certainly be in the interest of a would-be blackmailer to frame the dependence in the most inescapable way they can.

Third, agent 2 would need to be able to model communicated dependencies sensibly no matter whether it has a concept of blackmail or not, but while how it models the dependence internally would have a bearing on whether the blackmail would be successful that's a separate problem and should have no influence on whether the agent can recognize the relative utilities.