There are some of us that don't use the Clark method and still get stones.
I have used a coffee enema and gotten out stones.
I have used bacon, yes real pork bacon, and gotten out stones.
I have used eggnog and gotten out stones.
I puked up the oo and lemon juice the first time I used it and have never used it since. I have been flushing for 2 years and still get stones. All colors. All sizes. All shapes.
Try it yourself and then take the stones to them and tell them you used lemon juice and oo and see if they say the same thing.