See the thread a couple of pages back titled "Volunteers wanted for experiment". This was with respect to the very same doubt/question you have.
As you'll see from that thread there is a well-known experimental proceedure to dispell the doubts you have. Basically you use a dye (e.g. red beet juice) in the OO/GF mixture. You still get the lime green bile stones, proof that it nothing to do with the oil.
You don't have to do it yourself - just read through the results others have gotten - look in previous thread for link to faq/pictures.