This is non-sequitur. The fact that value derived from labour is required to exist for value derived from trade to be generated does not mean that either category of value is less real.
Labour gets you from 0 to 1. Trade gets you from 1 to 100. Labour generates value by adding to what's available. Trade generates value by multiplying what's available. The observation that zero multiplied by anything is still zero does not invalidate the fact that multiplication is still more powerful than addition. It just means that one cannot exist without the other if you want to have more than zero.