>>45513709They did it for "type diversity", completely forgetting that there is a whopping 12 fully-evolved mono-Fighting types and no Fighting/Water types in the base game and all 4 new Fighting types are monotype (or whose base form is monotype).
Making aquatic animals not Water type is fine, but given the circumstances Grapploct was a horrible pick for the trend.
Honestly, it would've been fine if they just gave it a second Ability that gave it a 50% boost to its Water attacks since it only has one, non-hidden Ability. But apparently that made too much sense.