Many dietary restrictions are a mask for mental illness. As are most vague health problems where no blood test reveals anything. Celiac and many 'allergies' are often self-diagnosed. Or the person lacks proper nutrition due to other foods they avoid. Such as low iron from lack of meat, hormone problems from soy consumption, excess carbohydrates or suugar. Gluten free and veganism are a control freak's dream because the diet requires obsessive micromanagement

At any rate, a Big Red Flag. Do not ignore. Proceed with caution.