Well, whatever "agreement" there was, the dissenting judge from the appellate court claimed that there was merit to Smollett's argument because he fulfilled his responsibility from it.

Judge Freddrenna Lyle dissented, arguing that “Smollett gave up something of value, community service and bond forfeiture, in exchange for a nolle of the whole indictment.”

I can only assume this is the main part of the appeal that the higher court is taking up.