…and both ways:

With identical seasons and performance, a preseason unranked team is more likely to be unranked at the end of the season and not make this list even though they were underrated… *because* they were underrated.

An overrated preseason team is more likely to still appear in the final rankings. As you said with USC.

In short:

-Preseason rankings are a somewhat-self-fulfilling prophecy as they inherently create final ranking bias toward their preseason choices.
-So this list only shows mistakes large enough to also overcome that bias.
-So the problem of misranking for and against those teams at the extremes is even bigger than what is shown here.