the increased flow helps flush the membrane to the waste line not through the membrane.
ino i think it is beneficial and according to manufacturers it does lengthen the life of the membrane.
if the increased flow doesn't help flush through it then its useless. I don't know about your unit but my waste line comes out from the membrane so the is no distance from the membrane to the wasteline
Additionally a helpful video from BRS. Installing a Membrane Flush Kit
Although its a how to installation video, it talks about the benefits of a flush kit and how it functions. http://youtube.com/watch?v=8i0oDBhu9Jc
The flush kit bypasses the flow restrictor pushing more water into the RO membrane housing which helps to flush out any deposits inside the RO membrane. Note the RO membrane is constructed differently than that of the sediment filter and carbon blocks. The membrane is constructed in a spiral. RO water permeates (passes through) the membrane while the waste water runs through the feed channel spacer of the filter removing impurities from the membrane (this is where the waste water comes from). Using a flush kit introduces higher pressure to the RO housing (the flow restrictor is after the sediment and carbon blocks) this help flush away some impurity buildup and extend the life of the RO membrane by clearing out the feed channel spacer. Check out this video which illustrates how RO membranes work.