They are not unrelated. As I've always understood it, brutalism was definitely about avoiding artifice, and exposing functional elements.
Wikipedia seems to agree. (An encyclopedia is a pretty good place to go for a common starting point when we're talking about what a term like this means!)
> Brutalist buildings are characterised by minimalist constructions that showcase the bare building materials and structural elements over decorative design…
> New Brutalism is not only an architectural style; it is also a philosophical approach to architectural design, a striving to create simple, honest, and functional buildings that accommodate their purpose, inhabitants, and location. Stylistically, Brutalism is a strict, modernistic design language that has been said to be a reaction to the architecture of the 1940s, much of which was characterised by a retrospective nostalgia.[29] Peter Smithson believed that the core of Brutalism was a reverence for materials, expressed honestly…
> A common theme in Brutalist designs is the exposure of the building's inner-workings—ranging from their structure and services to their human use—in the exterior of the building…
https://en.wikipedia.org/wiki/Brutalist_architecture