The text of the TPP basically ensured a "special trade relationship" between signers that outside, non-singers, would not be able to compete with. I would re-read the text of the TPP and see for yourself. It was basically a group trade agreement that guaranteed favorable exchanges. It's not that technically, they wouldn't be able to trade with China, but practically speaking, there was little chance.
I did read the text of TPP and it still isn't clear how it would have guaranteed that signers would not continue trading in large part with China. What I'm looking for is an actual economic analysis showing that TPP would have made it so that not trading with China carried a significant cost benefit in comparison to utilizing its market efficiencies and lower costs. I've yet to see such an analysis from a credible source, so I'm still working under the assumption that signers would have continued trading with China without any significant checks on its economy or policies.
I don't think anyone credible ever thought it would stop trade with China.
I think the dependency argument is more that if there is more trade between countries within the TPP system, it would have given China less policy strength because countries aren't as dependent on it.
If a country makes a large amount of their export income from a single source they are very vulnerable to policy blackmail by that country.
