Not being what one purports to be
He was ambidextrous because he could use his left hand as well as his right hand.
He could play the trumpet with either his left or right hand because he was ambidextrous.
She could only sign the document with her right hand because she was not ambidextrous.
However, it was as of 2004 commonly believed that babies are born ambidextrous.
I couldn't get used to them because I'm right-handed and only 1% ambidextrous (I can LOOK left with no problem).