I think an important piece of information that is missing from the experiment is the name of the vendor who he purchased the tabs from. For those with an interest in high-quality LSD, Silk Road was the place to go, and certain vendors were repeatedly tested, both laboratory-wise as well as via trip-tests.
(Let me take a moment and say RIP to SR; legitimate, multilayered good-faith efforts at harm-reduction were just dramatically reduced.)
But continuing, knowing the vendor, as well as his overall reputation, would add credence to the 100ug assumption.