I have a bit of a different view, Joel. I think a low-squirt shaft can be a disadvantage on the break in certain circumstances.
On a normal break shot, the player often tries to hit on the vertical axis of the cue ball rather than trying to apply side english. Because of the force of the stroke, however, he often does hit left or right of center. In essence, the player is unintentionally applying back-hand english to the cue ball.
In such cases, it is nice to have a break shaft that has a pivot point at the spot where the bridge hand is placed. Then, the unintentional application of back-hand english during the break shot would result in squirt compensation that still sends the cue ball in the direction originally intended.
A low-squirt shaft has a pivot point that is farther from the tip than the pivot point would be on a regular-squirt maple shaft. So someone who employs a fairly short bridge length on break shots would have his bridge hand at a point that is closer to the tip than the pivot point of the shaft. The result is that a break shot that is lined up on the center axis of the cue ball but is hit off-center on the cue ball will not have a normal back-hand-english type of squirt compensation. That is, it will not go where the breaker was intending, but, instead, will essentially be "over-compensated" for squirt and will go to the left of the target if the cue ball is hit left of center or to the right of the target if the cue ball is hit right of center.
On the other hand, someone who uses quite a long bridge length on break shots might find that a low-squirt shaft does provide good squirt compensation for the unintentional application of back-hand english (because he would be bridging approximately at the shaft's pivot point).
Also, I think a low-squirt shaft is an advantage on the break for players who, for whatever reason, cannot or do not line up on the center axis of the cue ball but do stroke straight back and through.