I've heard about line pressure a lot, too. Line presure is less in drive and OD than 1st and 2nd. If the line pressure "isn't enough" damage can occur. Somebody is kinding themselves if they think manually shifting their trans from 1-2 or 2-3 is doing it or the rest of their car any favors. For a car running 8's in the 1/8th mile will the extra line pressure really matter?
Is high line pressure more important than missing a shift, over shifting into OD or neutral? Somebody will need to prove that one to me.