The intention with the Bohrok logo was to capture the folded shape of the Bohrok and at the same time draw on design references from the old Egyptian icon of the scarab that rolls the sun across the sky. The big round shape above the midline symbolises above ground and the big Bahrag queen and the 6 layers underneath shows the 6 different kinds of Bohrok hibernating underground.
Since the Toa and the Bohrok basically originate from the same place this chart shows the hierarchy of the two different evolutionary routes. It was never used because it would get to close to telling the big secret about Mata Nui.