It's symbolic and sends a message to people who are still alive, similar to posthumously awarding a medal. You're saying "not only do no longer consider this a

It's symbolic and sends a message to people who are still alive, similar to posthumously awarding a medal. You're saying "not only do no longer consider this a crime, but we no longer consider this to be a crime to the degree that we are willing to rewrite the record". It may well give comfort to both surviving family as well as send a signal to other british homosexuals who are concerned about the security of their rights.