The only rudiment I know conceived of purely to make playing a certain rhythmical figure less complicated.

Stutter fives refers to how it feels to play a fivelet with a broken play phrasing. It looks like this:

R  R  R  L  L  |  R  R  R  L  L  ||

|_____5______|   |______5______|

and when you are learning to play it, it is difficult to line up the precise placement of each note against a subdivision of five against one against four.