They do not claim proof here. Further, they cite two other bunches of photons that "Two other short duration photon bunches bolster the statistical significanc

They do not claim proof here. Further, they cite two other bunches of photons that "Two other short duration photon bunches bolster the statistical significance of this limit" Every result, except for those whose environment is completely fabricated (such as in pure mathematics), is a statistical or probabilistic one. The question here is if their data is significant or not, and if they have made any mistakes analysing it - not that they only had N=1.