Onspeed, I have used similar approaches with our fast bowlers when bowling volume increases are starting to meet the increases in intensity (ball speed & run up velocity) during preparation blocks. (LxS stress is a big risk factor with this type of athlete)
I find it is a nice way to keep up the stimulus to the posterior chain while reducing compressive loading to LxS as well as reducing pelvic shear from excessive unilateral loading during this tricky crossover period with skill progression.
Not sure about the application to scrummaging, not exactly my area I am afraid. Look forward to further discussions on this type of stuff. Keep up the good work,
Aaron