That's not true at all. I know a man that can't spell for crap. His handwriting really looks like egyptian heiroglyphics (it really does, i mean it REALLY DOES.) He has been very successful in business. He retired recently to his 600 acre farm in the country, and sold his store inventory for close to 2 million. He spells secretary as secretterry.
Anyway you get the idea, spelling has nothing to do with it.
“If I should really WANT to answer the foolish question you have just asked, or any of the other questions you have been asking me, let me remind you that I have a row of electric push-buttons on my desk, and by pushing the right button, I can summon to my aid men who can answer ANY question I desire to ask concerning the business to which I am devoting most of my efforts. Now, will you kindly tell me, WHY I should clutter up my mind with general knowledge, for the purpose of being able to answer questions, when I have men around me who can supply any knowledge I require?” -- Henry Ford on the witness stand in a libel suit against the newspaper who called him an ignorant pacifist, as Quoted in Think and Grow Rich