Atually, in 1963 a 16-year-old could well NOT be aware that MLK wasn’t actually IN the Martin Luther King Freedom March that he was in.
Of course, it could also be that the march was in July I guess — this story has not entered in to some bizarre world where we can’t even pin down basic facts. Apparently multiple book and newspaper writers at the time couldn’t even figure out what MONTH King was marching, and yet you seem to think the entire nation was personally aware of EVERY march King was ever in.