Ahhh I understand - that’s a good point. Many people follow the low FODMAP diet without the direction of a dietitian (against the recommendation on how to do it) and likely aren’t getting the full result so GDH will still provide benefit, as well as helping the psychological side of IBS.

Interestingly, it’s possible they both help with visceral hypersensitivity - FODMAPs ferment in your gut causing gas and your gut to expand and hypersensitive nerves could then be alerting the brain to potential (but false) danger, so by avoid FODMAPs you avoid this process. Hypnotherapy could potentially be coming at the same process but from the top down instead.