Well, here's a guess, based on what I've been told by more than one manufacturer, and not just about rimfire ammo:
Demand is so high that even stepped-up production of .22 ammo (or powder, bullets, etc.) isn't filling demand--including orders from retailers. Thus when supplies come in, the companies send as much as they can, proportionally, to everybody on the list. Nobody gets everything they ordered, but the companies try to send everybody something. The big retailers, like Midway, get enough to fill SOME of their numerous back-orders, but not enough to list for general availability.
However, at one rimfire company they've actually cut back what they send to SOME brick-and-mortar stores. As an example, when they sent a pallet of .22 ammo to one store (the store's usual 3-month order) the store didn't put any limit on how much each customer could buy, so sold out the 3-month's supply in 3 days. And when customers complained about lack of supply, the STORE told them it was the ammo company's fault, that they weren't sending as much ammo--which was blatantly false. Whereupon a bunch of customers called the ammo company to whine.
So yeah, some stores may be getting less than others, because they pissed off an ammo company.
In fact, I am surprised so many ammo, powder and bullet manufacturers have been so patient during this entire "shortage," both with various retailers (who blame the entire problem on manufacturers that are making and shipping as much as possible), and some customers complaining that there's a supply-line conspiracy, solely to raise prices.
