I can't speak to kitesurfing, but getting started in windsurfing does not demand physical strength if you begin with good technique. Most beginners try to push and pull and work against the rig, and therefore make it a struggle. Using the legs, and keeping the sail balanced are the solution to the struggle. Unfortunately, it seems to be human instinct to do it the hard way. Another problem is that some people try to learn with heavy wave rigs, rather than light and easy trainer rigs. Just because the sail is small, does not mean that it is light by any means!
In observing kitesurfers learning their sport, I can see how the lift of the kite might make it feel that it involves less strength.
hope this helps,