I didn’t read your post in depth, but I do not believe it at all. I am very much right-handed, and my left hand is much more secure, has 96% percent of the facility of my right at least, is stronger etc. Having more facility is not an advantage. If my left hand played all the melodies, like your right hand might feel, it would be so eloquent and expressive. Perhaps you should watch the movie “My Left Foot.” It’s just not a big deal. I don’t think it affects anyone’s chances in competition. Most harpists neglect to develop their left hands enough anyway.