There is no middle. Yes, these are people who do not match through the main match algo. SOAP is a supplement to the main match that is run by NRMP to match unmatched people prior to Match Day, at which point they are "matched." People who are not matched on Match Day are "unmatched," and then have to fend for themselves.
The hot topic for the past month has been what the pre-SOAP match rate is at various schools, because that number is obscured, everywhere, by the final match numbers that include SOAP. I am pretty sure Drexel did not actually publish its pre-SOAP number as its final match number. I know for a fact that about a dozen other schools I have checked do not do this, and in fact refuse to release their pre-SOAP numbers, because, to them, the only thing that counts is the final number.