I’m really not sure what or how they achieved this but I’d love to take more photos of certain parts for anyone who is curious. I was shocked to see a perfect 90 degree reading from one of the flat holes on the sides of the diff cover (I used the hole closer to the driver side).It's possible they've changed something in the 2021s to get that caster up, maybe a slight difference in the LCA mounts perhaps???
They know low caster w/ Rubicons has been an issue and rather than giving them the proper LCA length maybe they've altered the mounts a bit to accommodate the old arms that apply to all JLs???
Otherwise maybe they might have to have a control arm recall for all pre 2021 Rubis???
I first thought they are using shorter upper control arms to bring caster back to 6ish degrees but I don’t think that’s very logical considering they wouldn’t even use currently extant longer arms they already make for their lift kits...