It’s also reasonable to look at it as a “the populace goes nuts every time there’s some minor shock to the logistics chain, so might as well prepare for that reaction”

Yeah, there doesn't need to be a shortage of toilet paper to cause problems, just the fear that panic buying might start so you better stock up before they hit. It's basically a prisoner's dilemma, you know you shouldn't panic buy, but if you don't and other people do it's rational to do it.

What would be a signal that you should panic buy to beat the rush? A drone shot down over Poland? Article 4 being invoked? What if a falling drone causes a casualty?

Simply having deeper stocks will let them avoid the empty shelf photos that can tip the balance into panic buying.