Narrowbodiedness is sometimes forced upon the living. Narrowmindedness remains a style choice available only to the human species.
This Hereroa glenensis is making most of the one-track rigidity imposed by its conditions. Not all weird options prove to be limiting. The branches grow where they may. Some plants end up narrowbodied, meeting vital requirements, and normal in all crucial aspects.
There was after all an old lady who lived in a shoe. And another who swallowed a fly. There is no end to what the living will attempt, given half a chance, or less.
In this way lifestyle definitions broaden over time, as living beings invent more options, by coping with what is imposed. Diversity is static neither in the growing of species, nor in their multifarious life adaptations.