I think you are entirely correct in the belief hoarding is an issue. Hardly a week goes by the rumor mill isn't stoked by something or other. Heard in November that the plant making Unique was transitioning to artillery powder, and it would not be manufactured for a ten month period. True? Who knows for sure? I do know my friend who told me about that story bought 24lbs of Unique because if it. Enough to last him eight years at least...
Compounding the problem is most all of the powder brands are essentially distributors of products doesn't help. If I recall correctly the only product Hodgdon manufactures is Pyrodex. Most everything else is imported from ADI of Australia, General Dynamics of St. Marks, FL, etc. Product suspensions are the result of the original manufacturer taking it out of production. Bofors supplies a good portion of Alliant's line, Lovex does for Shooters World, Valleyfield for IMR, Clermont for some Ramshot types, etc.