Luke,

I did read up on the pitching rules and balks. There is a clause about throwing an "illegal pitch" with the with the bases unoccupied:

(d) If the pitcher makes an illegal pitch with the bases unoccupied, it shall be called a ball unless the batter reaches first base on a hit, an error, a base on balls, a hit batter or otherwise. *** An illegal pitch is a quick pitch or a pitch made while not in contact with the rubber. Defacing the ball is illegal but not an illegal pitch by this definition. ***

I do remember not being able to do what's called a "quick pitch".

In a nutshell, illegally pitched balls with the bases unoccupied are called offically "balls" (unless the batter was able to get on base via some other method during that play. If called a "ball" and this is a fourth ball, the batter is awarded first base. Not directly because of the illegal pitch but because of the 4th ball in the ball/strike count.