We don’t always know what a design is intended to convey. We don’t always recognise or relate to a design’s intended user groups. But we don’t have to know everything that an object’s design is intended to do, in order to make effective use of the object.
I imagine the metal inserts in the wooden banister (see the video, above) are detectable warnings for people who are visually impaired, but that’s only a guess. If you watch the video again, you’ll see that the metal inserts do not occur at every bend in the staircase.
Whatever the intent, the banister fully met my needs.