Denial of class certification does not merge into a stipulated settlement for the purposes of appellate jurisdiction over a challenge to the denial of class certification as an element of the final judgement.
https://www.ca10.uscourts.gov/opinions/17/17-2029.pdf
Since 2011. An occasional commonplacing of the U.S. Circuit Courts of Appeal.
Neither an authoritative statement of the law nor legal advice. Quick work.