I had this exact same thing happen with the SST version. I selected the wait option (selected the latest date as possible) and it shipped the next day.
Mine shipped, it said it was backordered a couple of days ago also. I’ve been sticking with the wait option and so far all of my back orders have worked out within about a week or less.
People said no earlier. It only comes with an 18650 sleeve. You typically don’t need a sleeve with a 21700. If you do need one it’s easy to use a piece of cardboard.
dont use 21700 cells… they are too long and will compress too much on springs… atleast on 2 different batteries it doesnt matter i tryied, u are not supposed to use much force to screw down a tailcap…