Your terminology is good and your description is clear. However I cannot replicate that behavior at least not in the current Premiere CC 2015 (9.0.2). When I adjust values in the Motion Tab they adjust in increments of 1 and do not snap to the starting value or to edges of other layers.
Snapping works in the timeline and is turned on and off with the magnet icon or with the S key unless you’ve customized that. But that’s not what you are asking about.
– Larry Asbell