Here's my thinking on bridge slotting:

It increases string break angle. Now, if I take that to a bluegrass banjo, players crank the tailpiece nose down to get the same effect. It creates a crisper, sharper tone 'cos more downward force is being applied to the bridge.

Bringing it back to acoustic guitar, the saddle is the banjo bridge

If break angle can affect one, why not the other??

-F