These are both brand-new items, so it’s not surprising that some glitches in the supply chain occur and not everyone has the switches. It’s also not unusual for there to be some shortages in the retail supply chain initially, as Leviton will likely supply their approved installers first.
Probably what this means is that the new switches have been more popular than Leviton expected, and they’ve run out of the auxiliary switches.
The problem should solve itself with time, otherwise you just have to shop around to see who has the auxiliary in stock.
(BTW, in my experience over the last three years Leviton is often out of stock on their own site. They really don’t want to compete with their professional installer channel, so they don’t keep a lot of stock on hand for direct retail sales. I wouldn’t read anything into that.)