Power vs. Efficiency

A retired NCAA swim coach I've quoted here from time to time has added another aha moment to my life-long lesson in swimming.  It was late in the summer and the morning sun was blinding as I tried some backstroke kicks.  The old coach was in the next lane and watching all us regulars as he is inclined to do.  He saw me weaving in my lane as I had my eyes closed to keep the sun out of my eyes.  He advised turning to my side with one arm extended, lifting my butt and kicking from the hip.  The first instantly solved the blinding sunshine/lane weaving problem as I wasn't facing the sun so directly anymore; the rest of the advice seemed odd as it virtually did away with my flutter kick.  "Is that for more power?" I asked.  "No more power," was his reply, "but you'll be more efficient."  He's right.  It took me a while to really get the feel for it as the whole position, leg kick thing was new to me, but after one and half months I can say, I go further with each kick than I did before.  Am I more powerful?  No, but perhaps with the strengthening of my core by lifting my but (back muscles here), and using my hips more (more core and more whole leg), I will eventually be more powerful.  Time will tell.