Difference between ⫾ (U+2AFE) and ⫿ (U+2AFF) in the context of Dijkstra’s Guarded Command Language?

Continuing https://tex.stackexchange.com/questions/435986/how-to-draw-the-box-of-dijkstras-guarded-command-language, what is the difference in the intended usage of ⫾ (Dijkstra choice, U+2AFE) and ⫿ (n-ary Dijkstra choice, U+2AFF) in the context of the Guarded Command Language (GCL) of Dijkstra? In other words, when do you use ⫾ and when ⫿ for typesetting GCL programs? Moreover, can you confirm or reject Barbara’s answer?

Related: http://latex.org/forum/viewtopic.php?t=32939