Periodic Videos actually made a video dismissing Mason's claims during the early stages of his research, and the clips shown are from that video and I believe an earlier one.
Do you have a link for that? I have watched all of the Periodic Videos and I don't recall such a video. The Periodic Videos team is very professional, and Prof. Poliakoff in particular is very open to saying "I don't know" if something is not well understood.
There's a bit more to it than that, even. Thunderf00t emailed Periodic Videos early on saying that the "conventional explanation maybe isn't quite right" and pointed out many discrepancies to them. Not too long after Periodic Videos references a "viewer question/comment (very likely that email)" about the sodium + water reaction in one of their videos, and Poliakoff dismisses this comment as if it was a perpetual motion machine that was proposed. (It really was a rude/arrogant dismissal).
I do study chemistry (biotechnology) myself, and I've been a follower of Thunderf00t pretty much from the beginning. The explanation for this reaction given in all textbooks, and taught by all chemistry teachers and professors alike, is that Na + H2O -> H2 + NaOH. Reaction is exothermic, Na melts, heats up and H2 + O2 ignites into a small boom.
Thunderf00t noticed that:
1. Reaction is just as explosive without oxygen in the air (No H2 + O2 boom).
2. Drop dropping the Na in water the explosion would happen within a few millisecond (not enough time for the reaction to produce the amount of H2 for the the size of the bang it creates).
3. While filming it in high speed he detected secondary flames 'poofs' after the initial explosion, this could only be explained by the H2 burning (and much more consistent with burning H2).
4. Under certain circumstances the sodium would release green vapour as it reacted (just unexpected, and possibly a clue to electron conduction bands and solvation stuff happening).
5. H2 only burns explosively in very specific ratios with oxygen (1:2 molar), otherwise it burns rather slow (the 'foof' kind of burn).
etc etc.