The ELA has 2 tubes, one slides into the other, not 3 like most other telescopes. so the kick goes in the top tube and when you change batts it stays put. There's a video in the ELA thread showing it changed from 18650 to 18350 modes. You can see how the kick wouldn't have to leave the telescopic tube. As far as the top cap being threaded, I would assume so, considering there is an optional larger telescopic tube, makes sense they would use the same top cap. Don't quote me on that, but so much thought has gone into this device I would be shocked if that wasn't the case.
EDIT: Just read up on the ELA and yes, the top cap separates from the center tube for easy kick adjustment.