Nerva isn’t a treatment, it’s a program that teaches people self-regulation skills and relaxation exercises that can help them self-manage their symptoms.
So I think you’re conflating two issues. Celiac is an absolute intolerance of gluten, whereas fodmap ibs is based on being unable to digest large quantities. No one really knows why, and it’s not implausible some mechanism such as stress reduction or hypnotherapy would help.
Whereas for a celiac no such solution would work, there’s a real inability to digest. Perhaps in your case this extends to some fodmaps, but gluten isn’t a fodmap.
Also fodmap diets are generally elimination + reintroduction.
So while the app is inapplicable to your case, you’re overgeneralizing from your case to all cases.
(I would of course encourage anyone with IBS issues to get a gluten test. It’s important to rule out!)