It is not a 1/100,000 of G. It is gravity exerted on one gram of matter. Easy to measure.
Making absolutely sure there is no electrostatic or magnetic or atmospheric or ionic force should not be too difficult with this level of force.
Moreover, there are times when nay-saying experts are wrong about new things. When the New York Times famously (and wrongly) debunked Robert Goddard's work and asserted that space flight using rockets was impossible, they did so in reliance on the views of scientific authorities in that era. As it was, Goddard had the better understanding of physics -- as did the German scientists and technicians who developed and extended his work.
With degrees in physics, work records in the nation's aeronautics agency, and a claim of a device that apparently works on a test rig, Buhler and his colleagues merit a hearing. In practical terms, that requires not a trip from Dayton to the dunes in North Carolina, but millions of dollars in outside funding to build a device and put it into orbit. Otherwise, as happened with Goddard and his rockets, a hostile nation may first reap the benefit of pioneering work by Americans.