I don't know all the details, but generally, fine particles in suspension are either positively or negatively charged and both need to be present to get these particles to settle out. WE kits have a one part clearing agent that requires the heavier settled particles to be brought back into suspension to somehow grab the finer particles and settle them out.
Some other kits, including Spagnols, use a 2 part clearing agent that allows this process to occur without stirring up the heavier settled particles.
As for other benefits from stirring up the lees, there is a process called battonage, that has the lees stirred up periodically over a few weeks, before stabilization, and this can increase the mouthfeel of the wine. I have only just started battonage for the first time on a wine, so can't comment on its result yet. There may be other benefits to stirring up the lees as well.
Cheers .. Doug