I'm gonna be that guy... but former English teacher here - By definition, factoids are inaccurate :) inaccuracies repeated so often that people 'go with it', that's when they become factoids.
'inaccurate factoid' is an example of a tautology. Like naan bread, or armed gunman.
If you're a former English teacher you should be aware that language changes and while "factoid" was originally coined to mean a made up fact, the term is currently mostly used to refer to small inconsequential facts.
Wouldn't it be a pleonasm? Tautology is more about the logic realm, specifically about repeating an argument or a statement as it they were different. Here "inaccurate factoid" is merely inaccurate vocabulary.