I would say the closed ground ends are important on the rebound spring at least, to minimise stiction and avoid pickup between it and lower surface of stub axle during steering input. Here any such stiction will be at its highest as the unloaded inner wheel on a turn will cause stub axle to come into firm contact with rebound.
Cain at Wolf performance realised this when he started offering his lower steering bearings which fit between the above mentioned. In a phone conversation I mentioned my scepticism of their worth so Cain offered to remove and refund if I wasn't immediately satisfied. The lighter steering after fitting was noticed as I left his drive and it was a no brainer to retain them when I later fitted the SSL kit.
Worth mentioning that Cain showed me the very obvious witness marks on both top of rebound and underside of stub axle before fitting, despite car having barely covered 3000 miles from new.
