There is a typo at ore-veins/README.md:
use_realitive_y (Default: false) If true, the y-values will be interpreted as an offset from the surface at each position. (i.e. min_y = -20, max_y = -5 will generate ore veins from 20 to 5 blocks under the surface)

Must be:
use_relative_y (Default: false) If true, the y-values will be interpreted as an offset from the surface at each position. (i.e. min_y = -20, max_y = -5 will generate ore veins from 20 to 5 blocks under the surface)