Cumulated Stroke means keep adding depth while holding the button of drawing instead of moving around.
For example, if you want to inflate a particular region, you have to draw around, sweeping around to trigger the stroke. Cumulated Stroke can let users skip this action.
it is much more important in the case of Cloth Brush because while your stroke is drawn out of the mesh, the simulation will stop.
Cumulated Stroke could kill this meaningless action! Just click and be still, stop until having result you prefer