With an adjustable clutch fork pivot ball, does making the pivot ball longer give you more or less release (that is, less pedal travel needed to release the clutch)?

The idea of an adjustable pivot ball is to get the correct distance from the head of the ball to the mating surface of the block. This sets up the fork geometry properly. It is not supposed to be used to adjust travel. But, to answer your question, if you make the ball longer, it puts the fork/throwout bearing closer to the pressure plate. That would give you "more release", but at the expense of losing your 1/4" gap between the bearing and clutch fingers at rest position.

I'm a little confused about this myself. Why would you need an adjustable pivot ball? It seems to me that the only difference it would make would be the length of the fork pushrod after the adjustment.

I'm a little confused about this myself. Why would you need an adjustable pivot ball? It seems to me that the only difference it would make would be the length of the fork pushrod after the adjustment.
I believe they are used if you are using a "scattersheild", since they are not always the same dimensions as a stock bellhousing.