I was told they had to. This is not true?
They don't have to put anything on the docket. It's their discretion and most of the time any documents that are submitted to the court are first reviewed by a group of their clerks...who then submit a summary to the justices who then make the final decision.
Broadly speaking, thousands of petitions are submitted to SCOTUS every year...yet less than a hundred are heard. Something like less than 1 percent. [1]
Point being, LOTS of documents (petitions, motions, etc) are submitted, with the overwhelming vast majority not put on the docket...let alone heard.