It's crap! lol Actually, left-handed people are more creative, because the right-brain controls creativity and also controls the left hand. No need for the brain to coordinate with the two halves to process the information and ideas = more creativity and creative output.

However, those who have trained their brains to work with both halves (aka whole-brain processing) are probably even more creative as they avoid the mental roadblocks caused by the primary use of one side of their brain.
(Can you tell I did some research on this?)