Don't take the names of the ratings so literally in HBD.
For pitchers, you shouldn't think of the velocity rating as speed, but as strikeout rate. A pitcher with a high velocity rating will strikeout more hitters than a pitcher with a low velocity rating, who pitches more to contact.
Likewise for hitters, the contact rating is more about strikeouts versus putting the ball in play. A low contact hitter will strikeout at a higher rate than a high contact hitter. I've heard the splits described as the ability to "drive" the ball. I suppose that means hitting line drives as opposed to routine ground balls or pop-ups / fly balls.