I am to the understanding that if you lift over 2", it is recommended simply to allow for lower arm drop for climbing and to allow for a more grounded camber when aligning. It also sounds like it doesn't affect wear on boots one way or the other though. Unsure about that bit.
On the flip-side, it really isn't necessary if you only decide to crank your torsion up less than the height mentioned above. I researched this on the forums again recently as well since I am considering cranking up about 1" in the front to remedy some sag and getting some tighter, more solid shocks (ya, I LOVE a hard ride). This is the conclusion I came upon from the information available, whether right or wrong, so don't take my word for it, heh.
Gary Noonan
'01 S/C VX / '18 Forester XT