It's a proof of concept. You always start small, ESPECIALLY when a clinical trial involves invasive procedures. You certainly would NOT want to subject a bunch of people to endoscopies (at least one at the beginning, and one at the conclusion) if you didn't have at least some evidence that it worked.

I think they were lucky to get 4 people to consent to this with NO evidence of efficacy whatsoever. Now that there is positive evidence it will be a lot easier to recruit people.