I found this from https://upgradedpoints.com/jetblue-boarding-groups/

JetBlue’s boarding procedure assigns groups for general boarding based on the number of passengers on the plane and where they are seated.
Your boarding group is based on the specific seat you are assigned to (not the row), and it’s designed to stagger passengers in each group so everyone has enough space to get settled.
Because of the way they do this, it is not possible to choose a seat to get yourself into an earlier boarding group. For each flight, the same seat may be in a different boarding group depending on the other passengers and their seating locations.