Kris
I was expecting the start and end controls to have some effect but they do not effect a dip to white or any other dissolve based transition, dip to black, film dissolve etc.
The preview panels in the effect controls area do update as you scrub the start and end points but the dissolve itself does not change.
You can try it for yourself drop a dissolve transition across 2 clips, move the play head to a point where you can see the transition happening between the clips then scrub the start and end controllers for the transition. The preview panels below the start/end controls show the effect of the changes but the it does not change the transition itself highlighted by the play head. The start end points have no effect on the transition itself only on the preview panel displays ?!
I would be grateful if you could try this and let me know if you have the same results or whether I have a glitch on my system.