I fly the 738. Once upon a time going into Salzburg we were well above the glideslope upon intercepting the localiser at Salzburg. The Captain selected LVL CHG and took the gear early and, if I recall correctly, landing flap. We had a non-standard rate of descent for a little while but were still stabilised by 1000' AGL. The only thing I could never quite figure out was why he needed to add so much extra thrust and speed. He said afterwards that it had nothing to do with drag, but was necessary to prevent the AP kicking out on capturing the glideslope. Anyone know why it would do that?