I’m confused by your post. USC does not offer Early Decision or Early Action.
For colleges that do, and especially Early Decision (which in binding) as much as 1/2 the freshman class is accepted from ED applicants. Your question, as I understand it, is what happens to ED (or EA) applicants who are not accepted early? For those who are defered and then rejected would they have done better by applying RD? At one level admissions looks at them twice. At another level they didn’t make the first cut. But then the admission rate for that first cut is much higher than for applicants who apply only for RD. We’ll never know.
What to conclude? If the college offers ED and you can afford the college (or trust that need blind colleges will make it possible for accepted students to attend – typically without loans) and the college is on top of your list then apply ED. Best is not to overthink the process.