Aspalathus spinosa subsp. spinosa branches elongate rather than clutter. Every large, upper branch is a busy producer of leaves, flowers and fruit, not inhibited by any dark shade that would be cast by too many (and longer) side-branches.
The urge to grow side-branches exists in the plant, but the short, lateral branchlets it produces bears only short-lived, soft items like leaves or flowers that soon disappear. Then they dry out and harden for transfer to the defence department, where they serve as the sharp spines that made a name for the plant (Curtis-Scott, et al, 2020; Vlok and Schutte-Vlok, 2015; Pooley, 1998; Bond and Goldblatt, 1984; iNaturalist; http://www.worldfloraonline.org).