Osteopathy is not evidence-based medicine.

There actually quite a bit published on osteopathy. According to the NHS:

There is good evidence that osteopathy is effective for the treatment of persistent lower back pain. The National Institute for Health and Care Excellence (NICE) recommends it as a treatment for this condition.

More importantly he's already using a non-evidence-based treatment when he drinks his liquor to prevent the stomach cramps.

I would doubt that their are good well powered trials that show how to effectively deal with stomach cramps that come up after getting your gall bladder removed.