Just stumbled on it while playing with mv. Checked the source code and found probably a typo. The arg alpha is unused and 1.0 is used instead. https://github.com/uncomplicate/neanderthal/blob/4a896bde840884a30a9ff8067a5a16bba441aab5/src/clojure/uncomplicate/neanderthal/core.clj#L1285

Thanks for catching this oversight! I fixed it in the newest snapshot (0.21.0-SNAPSHOT).