I mean, it is a hard line elimination diet. If you watch what happens with reintroduction, you can provably figure out where the issues are.

Yup, but getting people to try it involve so much effort you only really do it for people you care about. It's amazing how resistant people are to eating only meat for a month or two, but drinking alcohol is no problem. Chemical preservatives? No problem. Added sugars? No problem. Seed oils washed in solvents? No problem.