That is my experience with my bentshaft.  I use both an ottertail and a bentshaft situationally.

The bentshaft does help correct technique, maybe compensate for poor technique is a better way to say it.  Exactly by providing a perpendicular face through the power phase.  I also find that when my technique gets sloppy while using the bentshaft I notice the loss of power a whole lot more than with the ottertail.

The bobbing up & down of the boat with a straight paddle is an indicator of technique problems.  The blade goes in vertical and comes out near the hip.  If I'm bobbing then I'm either not getting a proper entry or my stroke is too long.  The latter is my usual folly.  There's something aestetically pleasing to me about a long stroke, but it's wrong.