Although I wasn't around during the 50s, this comment seems likely to be revisionist history to me. The article itself quotes Oppenheimer as writing (unsolicited): "He is by all odds the most brilliant young physicist here, and everyone knows this." and 'Wigner said, "He is a second Dirac, only this time human."'
I wonder if perhaps this opinion of Feynman as a showman has gotten more popular over the decades as Feynman and the physicists who knew him passed away, and more and more of us are exposed to him only through his lectures and books. (If you'll excuse an aside: a bit like Bill Simmon's thesis on the basketball greats Bill Russell vs. Chamberlain -- those of us looking back on history, with only artifacts, may draw conclusions that would be ridiculous at the time.) I don't know if this is the case, but it's a fun speculation.
I wonder if perhaps this opinion of Feynman as a showman has gotten more popular over the decades as Feynman and the physicists who knew him passed away, and more and more of us are exposed to him only through his lectures and books. (If you'll excuse an aside: a bit like Bill Simmon's thesis on the basketball greats Bill Russell vs. Chamberlain -- those of us looking back on history, with only artifacts, may draw conclusions that would be ridiculous at the time.) I don't know if this is the case, but it's a fun speculation.