Right or wrong, they committed a crime at the time. A change in law doesn't really invalidate the crime committed. That differs from this where the conviction itself was based on faulty evidence or procedure.
Just for clarity sake, I don't really agree with this but I do think it's a valid difference between the situations
This is the first launch of the program and they're still in a pilot phase. It will presumably roll out to more states (maybe all?) Next year