Merits of the request aside (because I really have no clue) how does this possibly help him?
Does he think the entire world is just going to forget he was originally convicted? That we are just going to go “Oh – there’s that guy who wasn’t ever found guilty of looking at child porn and doing sex things with kids”?
Do people who are convicted of stuff then acquitted on technicalities really think that the public just forget all their past crimes because a piece of paper says “sorry – they were prosecuted one day too late”?