It's actually a "test" being done for DHS/CBP for the government to more comprehensively monitor and control the travel of persons in the US.
Delta and JetBlue seem to be in government-kiss-up mode, and this "JetBlue-testing" is but an effort by the government to enable/implement a more comprehensive surveillance/control state applicable to passengers. The government should be thankful that the airlines are such kiss-ups to governmental demands/pursuits.