Why does everyone forget an odd coincidence about this show?

In the "Summer of 45" episode the writers had a band performing for the Manhattan Project atomic bomb scientists. They had Les Brown and His Band of Renown doing a secret show for them. I think the writers just picked it out of the air as a band who could have done such a show at that time. After the episode aired it was declassified and publicly released that Les Brown and His Band of Renown did do a show in real life for the Los Alamos scientists in 1945. This is supposed to be one of sci fi's greatest coincidences.