Why Iran's government would act in the way of logic, I can only guess. Most likely to placate the US and buy some more time to develop its nuke.
Case in point, as the Wall Street Journal reports:
According to Mr. Khorramshahi, the judges explicitly stated in their verdict that Ms. Saberi could be released because "there was no animosity between Iran and the United States."
"No animosity". Who do they think they're fooling, with their clown of a president talking shit about the US everyday?
Either way, Ms. Saberi is free to leave Iran. Thank God for small miracles.