Continuity Cops

The Legion had not heard of Chloe Sullivan (see here) and also were surprised to find Clark without tights, flights or glasses. Rokk thought that maybe the real Clark differed from his legend but the explanation was that Clark had not yet become the costumed superhero with a secret identity.

In post-Crisis continuity, the "Superboy" period of Clark's career was a legend so the Legion looking for Superboy would not have found him but the Time Trapper, for mysterious reasons, created a pocket universe with a Superboy and directed the time traveling Legionnaires into it. This is called "saving the appearances." There were several other instances of this post-Crisis:

multiple Earths existed until everything changed in the Crisis (that sounds like a fantastic reflection of Earth Real - "everything changed after the War");

Power Girl was not Kryptonian and Kal-El's cousin but Atlantean and Arion's granddaughter;

even J'onn J'onnz's green humanoid form was one of his metamorphoses;

Black Canary, not Wonder Woman, was a founding member of the JLA (later they changed continuity back again!);

the energy displaced in the Golden Age became the Young All-Stars, including the son of Hugo Danner and a new mother for Fury literally possessed by the Furies;

a new origin had to be found for Wonder Girl who had been a continuity anomaly in the first place.

DC are about to commit the biggest continuity crime of all with the Batman finding the Smiley button in the Cave! Who watches the watchmen?