If the gun maker is targeting a particular weight, an ounce is an ounce wherever it comes from. Of course, where the ounce comes from affects the balance. Depending on the density of the wood, it takes much 'hollowing' of the wood to add up to many ounces, most likely, just a few.
But, to answer your question, I don't usually tear nice guns apart to find out, but I have seen/owned lightweight Flues guns with solid stocks.