People skilled in alchemy or formations were called Spirit Alchemists and Spirit Formation Masters.
But, why didn't they just call them directly Alchemists and Formation Masters? It was because they always called them in such a way from long ago, and 'Spirit' was just their grade in those two domains.
Spirit Alchemist was alchemists' first realm, and once a tenth-grade Spirit Alchemist advanced further on, he would become a Heaven Alchemist, and Immortal Alchemist, Divine Alchemist realms were behind it.
It was also the case for formations as what was behind spirit grade formations were the three grades heaven, immortal, and divine ones, who possessed great might.
However, such grades system was too huge, and most people would pass their whole lives just in the spirit grade, and the 'Spirit Alchemist' title gradually replaced 'alchemist'.