[tzs]

It didn't say their exam was an entire postgraduate exam. It said they passed an exam consisting of questions from a postgraduate exam.

I'd guess that if someone tried to take the entire exam it would include things that do require "complex math" (whatever that is). But you don't have to get to the parts of QM that require such math in order to cover things that exhibit the meat of QM, such as superposition, entanglement, and uncertainty principles. I'd guess that it was those kinds of things covered for these students and that is what they were tested on.