He doesn't have ALL the power as the girls could team up to go against his wishes. But if he would have selected Tori to join the tribunal, the whole house would know with near 100% certainty that Tori is going to throw herself in. When it comes time to a house nomination, they may want to throw Jenny or someone else who is strong in just to mess Tori up. Granted that puts risk at Tori and Jordan picking one of their nominated 3 instead and now you have to face Jenny.
By putting Jenna in the tribunal, he and Tori at least have the knowledge of seeing who the house throws in in first before making their next move. Nany survives purely on politics and seems doubtful she would ever throw herself in. Jenna is all over the place mentally at the moment. Sure she could decide she wants to go in, but Jordan figures its a very low probability as she just said she wants to stay and usually stays away away from conflict. If i had to guess, there was probably an off camera conversation we missed where Nany and Jordan may have made some deal that lets Nany stay in Jordan and Tori's good graces and have her protected if she plays along with Jordan's plan. Thats the only way I can see Jordan being so confident that he's still in control.
By putting Jenna in the tribunal, he and Tori at least have the knowledge of seeing who the house throws in in first before making their next move. Nany survives purely on politics and seems doubtful she would ever throw herself in. Jenna is all over the place mentally at the moment. Sure she could decide she wants to go in, but Jordan figures its a very low probability as she just said she wants to stay and usually stays away away from conflict. If i had to guess, there was probably an off camera conversation we missed where Nany and Jordan may have made some deal that lets Nany stay in Jordan and Tori's good graces and have her protected if she plays along with Jordan's plan. Thats the only way I can see Jordan being so confident that he's still in control.