Perhaps it has to do with the microflora from the commercial Perique. I am not too convinced though because I don't see how whatever microflora would permeate throughout the leaves and barrel, even with a lot of mixing, to catalyze something in the raw leaf.How would that work? Perique is a process of using pressure on carefully prepared and rotated leaves over a period of time.
@cosmicfolklore you mention wine and sourdough, the difference is that in both there is a lot of mixing done to spread the starter throughout the mix, I don't see how this could happen in pressed tobacco leaves. Perhaps mixing redistributes the juices which would carry whatever microbes are doing part of the work. There could be something to it.