It is possible there have been a few cases where the defendant pleaded guilty, and then the prosecution dropped the charges.
However, no such cases like that were cited that I have seen.
More important, this appears to be the first case ever where a presiding judge - Sullivan - has refused to automatically accept the Petition for Dismissal.
Trump has appointed 3 judges to the D.C. Circuit Court...
Rao - voted for Flynn.
Katsas - I assume voted against Flynn.
Walker - has been confirmed, but apparently has not been seated.
Trump's appointee - Katsas - did not participate in this appeal. I assume some kind of conflict?
Katsas was confirmed 50-48, so it looks like the Political Left truly hates him.