Unlawful Flight to avoid a sentence is in itself a crime. Nowadays, the usual procedure is to sentence a bail-jumper in absentia. I don't know whether that was done in this case.
Remember, it was Roman Polanski himself who vitiated the plea deal by running. Now, he could as easily get a very harsh sentence as a slap on the wrist. Indeed, he could get more time for thumbing his nose at the court than for the admitted rape.
I shoulda read your post first. You make the point I wanted to make.