Just guessing: I would say not enough because the sample is extremely small and there is chance that the electrons jump from each sides of the probes, skipping the sample ? (like a short-circuit) + the fact that the probes themselves are not superconductor, so there is a natural accepted tolerance in the measures (claimed to be due to the probes)
If the video is to be believed, the samples shown are huge compared to a, trivial to make, pulled or cut platinum wire probe. You could just put it on a plate in an SPM and measure it.
So many questions. I assume this is all possible but they are focussing on one thing at a time to duplicate the results, if possible.
