This is not correct. Keeping the cue tip moving in a straight line requires a "piston stroke," not a pendulum stroke. A piston stroke requires coordinated (constantly changing amounts of) elbow and shoulder motion. This is much more difficult to achieve than an elbow-only pendulum motion, where the grip hand moves in an arc, which causes the tip to move up at during the back stroke and down during the follow through (assuming the cue isn't being lifted off the bridge with a "death grip").
Regards,
Dave
See, I think this is opinion / conjecture. It's not always easier. The piston/drop motion is a natural motion that takes less effort. If it were easier, everybody would be doin' it. The pool world isn't stuffed tight with players doing things the hard way.