I thought the same thing about the wax Mike. I also do a little dinghy sailing and that is where I got the advice from. Some of the old timers told me about it.
I did some time trials with wax, over a set distance, then stripped it clean and used the Rain-x. My speed did increase while paddling (went a greater distance over a set time at a constant speed). Still couldn't believe it so also did some trials with the sail,same as above (in another kayak, with a steady light breeze), and the speed and distance did increase over a set time.
Your thoughts on righting after a capsize could be correct though, this stuff does make it really slick. Using the long string polymers is interesting but I've never tried this.