My wife has had to follow a low FODMAP and gluten free diet for the last 6ish years. It’s miserable and I wouldn’t wish such a vast allergy as this on anyone. I know there are plenty of haughty taughty vegans in this thread making jest, but these kinds of allergies fucking suck and I guarantee vegans consume shit that has these compounds without even realizing, since like you said, it exists in far more than just basic meat-based foods.